When everything closes, are you sure that’s the lock screen and not the login screen? It sounds like cinnamon is crashing, which means you’re automatically switched back to the display manager (login screen). This can sometimes show the boot logo while it’s switching, happens on my laptop as well, noy sure why that is.
If it is crashing, you might find the cause in the logs, run journalctl -e
and dmesg
to check for errors
Does “Database > Merge from Database” not work for your case? I remember it helping when I had a similar situation