Safe Mode is a special execution mode that you can use to troubleshoot issues in Thunderbird.In Safe Mode, you can reset some settings and disable add-ons that might be the source of the issue.
Clicking on Troubleshooting Information in the Help menu opens a new tab that contains plenty of information to help fix your problem.
This section lists all of the add-ons to Thunderbird.
You can see whether add-ons are enabled or disabled status, along with the version of the add-on. This section provides details on the graphics chip and driver version being used on your computer.
You can migrate your settings files (emails, feeds, or newsgroup messages) one by one, checking each time to see if the problems resurface.
If you do find a particular data file causing a problem, you can report the bug and attach the associated file.