I found three previous threads about this issue or yours. It seems that this has been an ongoing problem for a year and 9 months now. https://support.mozilla.org/en-US/questions/1110344 https://support.mozilla.org/en-US/questions/1067958 https://support.mozilla.org/en-US/questions/1037358

I have just reviewed all those threads, and IMO you have been resistant to providing requested information at times (r.e., Crash Report ID's), you have ignored suggested actions or diagnostic procedures (r.e., creating a new Profile for testing purposes), and a few other items that sound like Windows OS issues (r.e., BSOD's, OOM conditions, and driver issues) that will affect Firefox.

Overall I wonder if your hardware is "up to the task" with the way you are using Firefox with having so many browser windows open; or if a clean re-installation of Windows might be beneficial.

I am going to tag this thread as "Escalate".

I had written a quick reply before I had dinner, but while I was proof-reading it, FF hung and crashed. And when I re-started it, one of my windows was missing,, so I had to Exit and restart FF.

FF crashes almost every day (or every other day), but those crashes are NOT related to this "windows vanish" problem, except in one respect. The fre4quent FF crashes cause frequent FF restarts, and thus more opportunities for windows to vanish. I have kept a log of "vanishing" windows and the causes of the re-starts. I have seen vanishing windows after FF crashes, after reboots (when, I believe, I have done a clean Exit before the shutdown), after clean Exits, and after i have cancelled FF via the Task Manager. So, I believe that the presence or absence of a sessionstore.js file (after a clean Exit) has no bearing on this problem.

I could run FF starting with one window and then start other windows when I need to switch to a new task. But then I( would not automatically have the desired tabs available to me. And if I close my windows, one-by-one, I probably would not be able to determine what is causing my problems. And, of course, if I ran FF with only one window, I can pretty much guarantee that that window will not vanish upon restart.

If my hardware is not "up to the task", then the problems I am experiencing are due to some limits I am reaching. I have run "sfc /scannow" and it shows only three (unused database) files that are faulty. In all my days of working with IBM mainframe software, I only had to re-install software two times.. One time was due to a translation table error in a remote card reader; the other time IBM and I could not determine what had happened during the installation. I do not know what a re-install of Windows 7 (along with all of the software I have installed) will do. One thing I will try soon is a memory test. It has been a while since I ran a test and found a bad stick of memory.

--Barry Finkel

I STILL NEED ASSISTANCE ON HOW TO DEBUG THIS PROBLEM. If my problem were to occur on a machine of one of the Firefox developers, I assume that that developer would not just exit and restart Firefox; that developer would use one or more available tools to look at the running Firefox and determine what happened.

What happened yesterday is this:

    Wed 22:56  FF crashed
    Thu 08:__    Restart Firefox
                        Look at 19 web pages before leave house at 8:30.
            20:46  Got back to computer, and FF crashed
            21:23  Notice FF started with 10 of 14 windows.  "Embarrassing" screen showed 14  windows,  Exit and restart FF
             21:30  FF started with 10 windows; no "embarrassing" screen.
             21:39  Exit FF and capture sesssionstore.js, which has 15 windows.
             21:45  Start FF but it has only 8 windows.
      Fri  08:00   Exit Firefox.  No sessionstore.js file produced.
             08:04  Start FF.  No "embrarrassing" screen, but all windows present.

Again, how do I gather information when this problem next recurs? Thanks.

--Barry Finkel

Firefox crashes, so why not give us some Crash Report ID's?

Please follow the steps below to provide us crash IDs to help us learn more about your crash.

The crash report is several pages of data. We need the report numbers to see the whole report.

1. Enter about:crashes in the Firefox address bar and press Enter. A Submitted Crash Reports list will appear, similar to the one shown below.
2. Copy the 5 most recent Report IDs that start with bp- and then go back to your forum question and paste those IDs into the "Post a Reply" box.

Note: If a recent Report ID does not start with bp- click on it to submit the report.

(Please don't take a screenshot of your crashes, just copy and paste the IDs. The below image is just an example of what your Firefox screen should look like.)

More information and further troubleshooting steps can be found in the Troubleshoot Firefox crashes (closing or quitting unexpectedly) article.

Here are the "Recent" crashes. I have not looked at any in detail. For another of my open problem reports I have looked at the "Modules" tab in each and noted the DLL files that are highlighted in red. I have noted that some of these dumps have common symptom strings. Unless someone with dump-reading knowledge looks at the dumps in detail, we will not know what is causing my numerous dumps. But those dumps are not the main reason for this trouble ticket - the vanishing windows are.

I looked quickly for the Mozilla document that describes the sessionstore.js process, but I could not find it. I would like to see the official documentation as to when the sessionstore.js, restore.js, and restore.bak files are created. I have done am Exit in FF, and the sessionstore.js file was not created. And I have had FF "misbehaving", I have left the machine overnight, and a few hours later FF has crashed. But the tabs on restart do not reflect the state of the tabs when I left the machine.

bp-be243b70-ce85-4a30-a8bd-df3e52160918 09/18/2016 09:49 AM bp-378557ad-f0ae-4b41-9ed4-1925b2160916 09/16/2016 03:42 PM bp-f998aeb2-d2db-4465-9957-ba7d32160918 09/16/2016 09:08 AM bp-7fbba849-3e4b-4ef9-9340-ce1712160916 09/15/2016 09:10 PM bp-2c51703c-1773-40ff-87e7-91e9d2160915 09/14/2016 10:28 PM bp-9477a6c3-b3d7-4546-868b-6f8102160913 09/13/2016 11:29 AM bp-d87a07d1-f5d8-4818-9ffe-61cf32160913 09/13/2016 10:03 AM bp-db128ec2-e6a4-43d4-8dbe-c35382160913 09/13/2016 09:16 AM bp-e33ee1b5-5858-43d6-a448-2d7792160918 09/13/2016 08:48 AM bp-a8444dec-41b2-4398-aaa9-0070d2160913 09/13/2016 08:37 AM bp-71721fa2-8e5f-4103-b8b9-e56242160912 09/12/2016 08:34 AM bp-a41289dd-1c6d-4ad1-9d7a-108962160909 09/09/2016 02:17 PM bp-44288035-f4e8-48d6-95ab-28c8e2160908 09/07/2016 08:41 PM bp-8e48429e-08d8-4cc5-8fc2-f2f132160908 09/07/2016 08:36 PM bp-3a8f0c31-7270-4fed-882d-8872c2160908 09/07/2016 08:07 PM bp-ac4df212-79a1-4446-a0ba-4b84b2160907 09/07/2016 01:04 PM bp-45e4964a-58fd-4465-84c0-0ea1c2160907 09/07/2016 08:08 AM bp-0213716d-c9d4-43aa-8a6f-39c322160906 09/06/2016 08:21 AM bp-44288035-f4e8-48d6-95ab-28c8e2160908 09/04/2016 09:28 AM bp-8e48429e-08d8-4cc5-8fc2-f2f132160908 09/04/2016 08:09 AM bp-e84eb841-f9bc-4987-8433-e7b512160902 09/02/2016 04:37 PM bp-65bba045-38cc-4347-88f3-d1b522160902 09/02/2016 09:51 AM bp-b20a15f0-53bf-44b6-a22f-cad442160902 09/02/2016 09:51 AM bp-47b7d1e1-3ef8-4052-8943-2f6052160902 09/02/2016 08:56 AM bp-503486d6-51a6-4450-b633-2413c2160831 08/31/2016 02:04 PM bp-8f93a2a5-91ac-4965-81b4-ceebc2160831 08/31/2016 09:46 AM bp-21e506b8-da77-41a3-a966-e46802160831 08/31/2016 08:46 AM bp-b4028aa7-f08c-40ff-b82a-d46b12160831 08/30/2016 09:46 PM bp-a5561fb1-308a-4848-a6dc-be9042160830 08/30/2016 03:09 PM

Also, the occurrences of the vanish problem I had 09/15 were:

   21:23  4 windows missing - after crash
   21:30  4 windows missing - after Exit
   21:45  6 windows missing - after Exit
   08:00  all 14 windows present - after Exit (no sessionstore.js)

I do not always look for a sessionstore.js file after Exit, and I do not always capture and process the sessionstore.js (if present) or the two restore.{bak,js} files, as ALL of the files I have captured and analyzed all have had all of my windows present. I assume that if the file used on startup did not have all of the windows present, then the missing windows would be lost, unless a bad sessinstore.js file was used on startup, but the restore.{js,bak} files were still intact and used after a subsequent crash.

--Barry Finkel

Here is something that just happened. I had been using FF for a while, and I decided to move three tabs from m,y main window to a window I call "SX". Copy one URL, paste it into the SX window, then close the tab in the main window. In the middle of this process, FF went into its "wierd" state, using lots of CPU and becoming "non responding" [whatever that means in Windows7 terms]. Then FF crashed. When I started FF, the "Embarrassing" screen showed 14 windows, but only 13 started. I then moved the three tabs from the main window to the SX window. One of the moved windows opens a short video. Then I did an Exit. There was NO sessionstore.js file saved. A restart of FF started only 12 windows. The SX window was not in the list of windows that had started, but a short video in one of the tabs I had moved started. That tab was no longer in the main window, and with the SX window not present, I could not go to that window to stop the video. I do not know what would have happened if I had gone to any window, opened a new tab, and entered a URL that was present in the invisible SX window. Would FF have told me that I already had an open tab with that URL and gone there if I had told it to do so? I will have to test this next time the problem recurs.

A subsequent Exit produced a sessionstore.js file, and a restart of FF opened all 14 windows.

Also, I have another question. I am not a good typist, and sometimes when I am entering a reply (such as this one), I hit some combination of keys that cause my entire reply to be erased. Do you know what combination of keystrokes causes this? This happened after I had entered most of this reply,, so I had to re-enter the text.

--Barry Finkel

Here is another update. Last night I had a 7E BSOD, and the machine rebooted. When FF started, it had 13 of my 14 windows. The window I use for computer-related tabs (such as this trouble ticket tab) was missing. I went to one of my saved sessionstore.js files to extract the URL from the first tab in that window. In another window I opened a new tab and entered that URL. I chose the option to "go to the existing tab", and the missing window came to life. So, now I know how to "recover" missing windows.

The object now is to determine why the "missing" windows are not being displayed.

--Barry Finkel

Is there an official Mozilla document (i.e., not in a reply to a forum question) that explains when the recovery.js and recovery.bak files are updated and written to disk? I have downloaded the 47.0.1 source, but it is so large that I am not sure where in the code to look to find the answer. I know that sessionstore.js file is written on successful Exit shutdown. Thanks.

--Barry Finkel

Have you tried using DXR it may help finding things

• https://dxr.mozilla.org/mozilla-central/source/
  • https://dxr.mozilla.org/mozilla-central/source/browser/components/sessionstore/SessionFile.jsm

You could file a bug for your problem, but I doubt it would receive attention because of your usual configurations. I do know of this

• https://developer.mozilla.org/en-US/docs/Session_store_API

But am not aware of documentation on the recent changes & improvements but there is an informative blog

• Firefox, the Browser that has your Back[up]
  https://dutherenverseauborddelatable.wordpress.com/2014/06/26/firefox-the-browser-that-has-your-backup/

   If sessionstore.js is valid, it will be used.
   Recovery.js will be used if present and valid.
   Recovery.bak will be tried next.
   Previous.js is then used to restore the session.
   And finally, upgrade.js will be tried as well.

There is probably little point in posting crashIDs in this forum for your complex setup and multi windows crashes.

Thank you for your reply. I realize that there is little point in my posting crashIDs to this problem record, but others who have offered advice have requested them. Now that I have a pointer to the portion of the code that handles sessionstore, I will look at it to try to determine the answer to my question. I assume that when my windows/tab configuration changes (but not if another sessionstore operation is in progress)), Firefox will

    1) Remove restore.bak
    2) Rename restore.js to restore.bak
    3) Create a new restore.js based on the changed configuration.

What I saw recently is this past weekend:

    Fri 14:55   TImestamp on restore.bak
    Fri 14:56   Timestamp on restore.js
    Fri             I worked with FF until around 17:00, and I assume that I opened and/or closed new tabs during those two hours.  I know I opened and closed new tabs based on e-mail messages in Thunderbird.
   Fri 17:00    Leave the computer
   Sat 19:30   Come back to the computer.  I do not remember what I did with FF, as MS Essentials was running a full scan on my computer, and everything was slow.
    Sat 22:44  FF was using 35% of the CPU and not allowing a clean Exit.  (This  is my other problem, but not germane here.)  The two restore files had timestamps from Fri 14:5_, so FF had not updated them in over 24 hours, even though my config had changed.
    Sat 22:53  Cancel FF via the task manager and restart.  FF had the configuration from Fri afternoon, not the config as I left the computer at 17 :00.

--Barry Finkel

I have a question. In the last reply it was mentioned that I could file a bug report. What is the URL for doing this? It seems to me that with my sessionstore.js file (or any of the restore files I have saved), a FF technician could start FF with that file, then do some Exits and restarts to reproduce the problem. I do not know if this problem would occur on a Windows 8.1 or 10 system, and I do not know if it would happen on a 64-bit system. I do not know if the problem is memory-related. My Windows 7 system has the max amount of memory that Win 7 32-bit can handle - 4Gb. Thanks.

--Barry Finkel

I did open a bug report - 1308593 - and with my sessionstore.js file the problem is reproducible.

--Barry Finkel

Correction - The bug report is 1308597.

--Barry Finkel