I'm having problems with Thunderbird 78.7.1 intermittently resetting my "prefs.js" file to what looks like a factory default. On these occasions, Thunderbird starts with a screen asking me to enter details for my email account. It is as though I had just installed it for the first time. When I quit without further action, I find that my "prefs.js" file has gone from 40 KiB plus to 3.5 KiB, the original having been erased. I run Thunderbird every day and this seems to happen about once every week or two. I don't know if it's relevant but, prior to V78, I had been having problems with being locked out and having to delete ".parentlock" to get in. I think this was to do with untidy terminations of the programme. Now the ".parentlock" file seems to remain in the profile even after a clean shutdown. This doesn't always result in my "prefs.js" file being reset. I'm running Thunderbird 78.7.1 (64-bit) on a machine running Linux Mint 20.1. The profile, calendar and mail daty reside on a local server running Ubuntu 20.04.2 LTS (GNU/Linux 5.4.0-66-generic x86_64). The mounting configuration line from fstab is: "//gannet8.local/Simon /home/simon/Home cifs auto,user,rw,gid=simon,uid=simon,vers=3.0,credentials=/home/simon/.sysaccess 0 3" Any ideas as to what could be causing this. I made a copy of my profile from when this happened this morning before finding a backup of "prefs.js". My concern is that Thunderbird seems to wipe out the "prefs.js" file without making a copy.