Can confirm this. It seems to be leaking memory. One CPU core is fully used and the RAM usage goes up to 90GB on my system. TB might respond to a mouse click every 3 minutes. Happens also with all extensions disabled.

This will also happen if you have the preferences page open in a non-focused tab.

Downgrading to 91.2.1 fixed the issue.

I downgraded back to 91.3.0. No issues. I think the developers do not check well what they release. Many problems arose for many users since the release of version 91. If problems continue like this, we will have to turn to another email client. DO NOT INSTALL/UPGRADE TO TB 91.3.1

Reading very old articles in Mozilla Database, I found out that the crash of memory arose after updating to version 91.3.1 was due to the language packs. I uninstalled them and then reinstalled. No memory crash or screen hung up. All is OK now.

I don't experience any freezes or hangs in 91.3.1/W10. I suggest testing in safe/troubleshoot mode, and if the problem continues, run Windows in safe mode. Check that there are no language packs installed in the Languages section of Tools/Add-ons, as these are known causes of Preferences hanging.

Safe mode with TB 91.3.1 doesn't fix the issue, even with all add-ons disabled. Also the memory leak keeps happening on the preferences page in safe mode.

Safe mode with TB91.2.1 works fine, the preferences page does not cause a problem.

Updating to TB 91.3.2 didn't fix the problem.

I can confirm that the last version not affected by this is 91.3.0.

> due to the language packs. Deleting all my language packs fixed the memory leak in the preferences page from TB v91.3.1+. Great finding!