I'm not familiar with SyncToy. However, if it needs administrator privileges to copy a file, would it work to use "Run as Administrator" with SyncToy?

You did make sure that Firefox was closed when you made the backup ? For the passwords you need logins.json and key4.db with the latter storing the encryption key.

Did you check the properties of the logins.json file ?

Do you possibly have security software that might be interfering ? What security software do you have?

You can check which process has a file handle on a file with the process explorer utility.

• https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer

Firefox was closed when I did the backup.

I have checked the properties of the file, I couldn't find anything odd about it.

I use AVG, but I don't see why it would interfere with a random file in firefox.

As for SyncToy, its a simple tool made by Microsoft eons ago that copies data from one spot to another and ignores unchanged data making copying data faster like when doing backups. I tried administrator mode as well, and other methods of copying too.

I checked for the file being loaded by any process in resource monitor.

For AVG and passwords, see:

• https://support.mozilla.org/en-US/kb/passwords-disappearing-avg-security-software

My passwords weren't corrupted, I just can't back up that one file. All my passwords still exist, the firefox database of passwords is still accessable within firefox. Its just that, logins.json is totally locked down so it can't be copied.

It's puzzling because people copy/paste the logins.json file all the time.

cor-el can provide a script to export your bookmarks as a "Plan B."

Oddly, rebooting fixed the file, I don't know how or why, but somehow when I rebooted, the logins file started to work again. I just don't get it, I checked everything in trying to find why the file was locked.