Hmmpff… This is going to be the first time I see a case where reinstalling Thunderbird might be worth a try. Have you tried that?

Thanks for your response, David.

I just closed Thunderbird, downloaded the current esr release, replaced the existing Thunderbird app with it, and re-opened Thunderbird. The symptoms remain.

My profiles.ini file shows two profiles although I have only one (I just deleted a beta profile). My profile shows "locked=1" even when Thunderbird is closed. Is that appropriate?

Check the prefs.js file in profile. This seems some form of corruption, possibly antivirus interruption or file in read-only mode. Also, check to see if there are multiple versions, such as prefs-1.js, prefs-2.js.

Macintosh, no user-controlled anti-virus app, only what Apple does in macOS.

There is only one prefs file. It is not locked. I have read and write access.

Should I restore my prefs file from a back-up?

What I read about "locked=1" indicates that it is normal.

Here's what has my attention: profiles.ini and installs.ini each show three installations although I have only one. In each case, two of the three installations point to the same profile.

I don't know when these symptoms first appeared. I wonder if it has anything to do with my downloading a beta release yesterday (and deleting it today). My main installation is the latest esr release.

What's weird here, and the reason I thought reinstalling might work in this particular case, is that it looks as if some form of corruption was present in the application itself, not in the user data…

I'm not at the computer right now and cannot give you more specific instructions, but this could be a missing font or some similar issue. Try restarting the Mac in Safe Mode and see whether the problem happens there as well.

The symptoms persisted in safe mode.

There may have been some other odd things in that profile, e.g., subscribed folders becoming unsubscribed or vice versa, or Thunderbird not respecting my setting not to show only subscribed folders.

I played with profiles.ini because of the extraneous installations, but gained no insight.

So I created a new identity, re-created my accounts, re-set all my settings, which was not trivial because of config editor changes, saved searches, et cet., and copied my local folders to the new identity.

Everything seems fine other than that I cannot import my certificate from the old profile. I will raise that issue in a separate inquiry.

DavidGG, I notice how active and supportive you are in this forum. I appreciate your help. I hope that other people do too. Solving computer problems over a discussion forum is not easy.

Ah, wait, I misunderstood… I thought Thunderbird was failing to properly display the account settings pane, but it looks like it's only the info that should be displayed there that was just not appearing or was disappearing from there, right? So everything I said was mistaken, sorry for the confusion…

So yes, it looks like there is/was something wrong with your profile. You may use the About Profiles Thunderbird built-in profile manager to help troubleshoot that, which is what you appear to be doing now…

DavidGG, yes, only the information was missing. All is good now. But, of course, one should not have to re-create profiles.

Yeah, but I for one have not seen something like that reported before. A possible cause could be the beta you said you had installed. Doing that without making a backup first is asking for trouble. Or if you had a backup, you could have tried restoring from the backup first before going all that trouble…

If it was a single account that was affected, you could have re-created just that account, but it was happening to all the accounts in the profile. Even if anyone knew which was the presumably corrupt file that was causing this, it might still have been preferable to fix it doing what you ended up having to do.