There is a known problem with Windows Search in Windows 10 causing freeze-ups in Thunderbird. To fix this:

Thunderbird Menu: Options: Advanced section: General tab (If you cannot see the Thunderbird menu, press the Alt key or F10 key on your keyboard to show the menu)

See my screenshot.

Uncheck/disable "Allow Windows Search to search messages"

Quit Thunderbird. Restart Thunderbird.

If you still encounter freeze-ups, we can try more things.

Thanks! Just did it. It'll probably take a few days before I know if it worked because it's an intermittent problem. Will check back. :)

By the way, why would the error message be about Chrome/messenger?

That error may have had nothing to do with your issue.

"imStatusSelector.js" has to do with the Chat functionality in Thunderbird. If you are not having any issues with Chat, then don't worry about it.

Didn't work :(

By the way, why would the error message be about Chrome/messenger?

In the context of Thunderbird (and Firefox), the chrome is any visible aspect of a browser aside from the webpages themselves (e.g., toolbars, menu bar, tabs). This should not to be confused with the Google Chrome browser.

In any case, the error has got nothing to do with your problem.

Didn't work :(

Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

AVG is known to causes intermittent Not Responding in Windows 10. https://support.mozilla.org/en-US/questions/1114834