onEndMsgDownload chrome://messenger/content/msgHdrView.js:803
   ThreadPaneSelectionChanged chrome://messenger/content/threadPane.js:415
   onselect chrome://messenger/content/messenger.xul:1
   MozTreeChildren chrome://global/content/elements/tree.js:65

I am using Thunderbird in a corporate setting with little corporate support (i.e. I can use it, but I'm on my own for problems) - I mention this upfront because I will not be able to perform certain troubleshooting steps (e.g. disabling AV). I also attempted an upgrade from 60.9 to 68.1.2 because I am pushed to always be on the latest version. I'm guessing it's due to maildir file storage which I need because AV cripples Thunderbird with mbox (as at the very end a new profile works, but defaults to mbox file storage). Archiving: After the upgrade everything seemed to work until I went to archive a message and later send a message. Upon archive the message disappears from the Imap Inbox where it was and an entry appears under the Archive folder for the current year (2019). Clicking on that entry shows the first image in the body. Clicking on messages that were archived with 60.9.0 show the body of the email normally. If I open my profile directory and go to the Archives.sbd > 2019 > tmp directory I find the email I just archived as one of the maildir'ed messages. If I copy that file (confirmed by opening it in a text editor) to the 'cur' directory the message body shows up when I attempt to view it. The only thing that seems possibly related in the Error console at this point is [1] below. Every other message is Lightning related as I have extra debugging on for Lightning for previous problems (and I never turned the pref off). Sending a message: I compose a message to myself (i.e. the same email address I am sending a message from) and click Send. The message sends and almost immediately I receive a dialog box titled 'Save Message' with the body: "Your message was sent but a copy was not placed in your sent folder (Sent) due to network or file access errors. You can retry or save the message locally to Local Folders/Sent-Local Folders. [Retry] [Save] [Don't Save]" If I click Retry, I get the dialog back (and a second copy of the message in my sent folder, but an empty body as in the image), if I click Save I get a new subfolder under Local Folders named "Sent-Local Folders" and a new dialog titled "Alert" and the message "Unable to save your message due to network or file access issues. [OK]". In the 'Sent-Local Folders' folder I have the message listed but no body (second image). My profile folder now has a new folder 'Sent-Local Folders' and there is nothing in the 'cur' folder, but there is one message in the 'tmp' folder. Opening it in a text editor it's the message from the previous paragraph - the plain 'Sent' folder in my Local Folders does not have a copy of the message. At this point I have a few copies of [2] in the Error Console. The errors persist if I restart Thunderbird in Safe Mode. I tried a new profile and it worked (i.e. the Sent message was copied to the Local Folder 'Sent' and an Archive action completes properly) but both the account I setup and the Local Folders in the new profile are mbox format, which doesn't work for me long term as above. Possible confounding issues: I used the mbox to maildir converter ~18 months(?) ago as antivirus was really bogging down archiving because it would scan on-access the entire mbox file when I tried to add to it. The maildir is much faster (and yes, my profile is many years old). I only have one profile, it is the default under about:profiles. My accounts are not sequentially numbered (account3 for Local Folders and account11 for my corporate imap, no other accounts). I need my email day-to-day so I am reverting to 60.9 for the time being but can swap back but it's a fair amount of waiting to restore profile backups so would like to minimize that. [1]: : Component returned failure code: 0x80550008 [nsIMsgDBHdr.markHasAttachments] msgHdrView.js:803 onEndMsgDownload chrome://messenger/content/msgHdrView.js:803 ThreadPaneSelectionChanged chrome://messenger/content/threadPane.js:415 onselect chrome://messenger/content/messenger.xul:1 MozTreeChildren chrome://global/content/elements/tree.js:65 [2]: Loading failed for the <script> with source “chrome://global/content/netError.js”. neterror:128:4