Try these:

Go to TB menu > Settings > General

- scroll all the way down and click the 'Config editor' button on the right

- click 'Accept the risk and continue'

- search for accessibility.force_disabled > change the value to 1 > click the check mark > restart TB

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Clear the cache:

- press Ctrl-Shift-Delete (Mac: Cmd-Shift-Delete)

- set 'Time range...' to 'Everything'

- untick all items except 'Cache'

- clear, then restart TB

Thanks for the advice. So far, so good!

I am using the same release and cannot duplicate the problem. If the problem continues, I suggest checking addons and possibly testing in troubleshoot mode.

Thanks for the advice. So far, so good!

Can you determine which of the two suggestions fixed it?

Definitely the change to accessibility.force_disabled = 1

I just set it back to 0 and the next e-mail I started hung TB almost immediately.

I do have an amendment to my initial report: it's not always the ' character that does it. It took about 3 days before I submitted this question, because I couldn't find a pattern. Some e-mails would crash within 20 words; sometimes it seemed like the spelling correction was doing it; other times it coincided with TB auto-saving a draft; other times, I would load a saved draft and TB would hang almost immediately when I began to type more words in it. But then I had an e-mail that crashed every time I tried to type the word "shouldn't" and I thought I'd found the trigger.

I had done both changes at the same time, so in order answer your question, I just a minute ago reset accessibility.force_disabled to 0 and started a new e-mail, and TB hung about 30 seconds letter, no ' in the text. I reset it to 1 and successfully sent an e-mail full of 's. So, I don't know what it is, but accessibility.force_disabled is the solution.

Should I file this on Bugzilla?

Not yet, as apostrophes are commonly used and I cannot duplicate this. To report that apostrophe crashes thunderbird would be difficult to test. Have you tried help>troubleshootmode? Addons can cause many problems. What you are experiencing seems very remote.

I have just noted that the ' is not the culprit. Also, from the first post: "The problem persists with Troubleshooting Mode enabled."

I suspected it was the cache, which had grown to 1GB in size, because this sort of behavior mirrors what I've experienced in the past when TB mail stores got too large or were corrupted, or when the programs tried to to access files or directories that had grown larger than anyone anticipated (e.g.,duplicating cookies instead of updating existing ones, and unable to read and process the 100,000+ cookies).

If I knew how, I think I'd look at a function that gets called only if accessibility.force_disabled = 0 and then check what files TB tries to access. I'll bet that one is corrupted, or exceeds the maximum size the software expects. Something like that.

1GB cache is not excessive.

Thanks for your efforts.

If you can supply the information mentioned at https://bugzilla.mozilla.org/show_bug.cgi?id=1972457#c27 it would be helpful.