After move to new computer (with profile) Thunderbird shows empty contents on 2nd open
moving to a new computer I was following the instructions at https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer
I installed version of Thunderbird 78.5.0 (64-bit) and copied my Thunderbird folder to %APPDATA%
Now on the first startup of Thundebird, everything looks fine (see on-first-startup.png), all my data and open tabs are as I left them, everything seems to be working.
Now I close Thunderbird (without having done anything) via X icon and start it again. It looks like on-second-startup.png, the tabs are gone. there is no content in the panes. The menus look strange, being partly empty (menus.png). Only the Help menu is completely there, however, the items do not seem to work properly (restart with addons disabled, e.g. does nothing). The about dialog opens but looks also strange (about.png).
I have googled and tried deleting global-messages-db.sqlite in my profile but this does not change anything. The file is created anew on Thunderbird startup, but the contents remain as above.
This is 100% reproducible. If I close Thunderbird, copy the Thunderbird folder into %APPDATA% and startup, everything looks fine. On second startup the same problem as described above shows up again.
Any help would be appreciated!