calUtils.jsm:127:15

I recently noticed that Thunderbird quietly updated itself from 102.15.1 to 115.3.1 for me today. (I'm on Win 10) After this, none of the emails in my imap.gmail.com mail account are viewable: My 'Inbox' shows 2 email accounts underneath and selecting the gmail one shows a big list of messages but opening (double-clicking) any of them just opens a new tab that remains entirely empty. Emails for the other Inbox account do correctly show messages in a new tab when opening, as things were previously. The Tools > Developer Tools > Error Console shows the following errors (after having first cleared the log and then restarted Tb) - NotFoundError: No such JSWindowActor 'DevToolsFrame' Assert failed: Calendar manager initialised calendars before loadCalendarComponent ran on the first 3pane window. This should not happen. calUtils.jsm:127:15 NotFoundError: No such JSWindowActor 'DevToolsFrame' I found recent posts for ''similar'' sounding issues (but not quite the same). One suggested deleting 'folderCache.json', 'session.json', and 'xulstore.json' files from my thunderbird profile folder and restarting. I tried and it had no noticeable effect. I can't be sure whether it was there before but after the problem update, I notice I have 2 instances of my gmail address showing under the 'Sent' tray/group. Under sent it lists 2 x my gmail.com account and my other account. Again, the other account's sent mails can be viewed just fine as before but the first '[email protected]' account list most (perhaps all) of my sent emails, but opening any of them just brings up a totally blank new tab again. Interestingly, however, the other (new?) duplicate '[email protected]' under the Sent group also shows a big list of sent emails and this one does correctly show all messages when viewing any in a new tab. The properties of both of these identical-looking 'sent' mailboxes ('x'-ing out my email) are - 1st - Location: imap://xxxxxxxxx%[email protected]/Sent Showing 267 sent messages Doesn't work. Viewing any of the messages just shows a blank tab. 2nd - Location: imap://xxxxxxxxx%[email protected]/%5BGmail%5D/Sent%20Mail Showing 283 sent messages Works. Viewing any of these opens a tab that correctly shows the message. To my knowledge, I've not added the second almost identical 'sent' gmail account. The location of the newly broken @gmail.com Inbox is - Location: imap://xxxxxxxxxx%[email protected]/INBOX The fact that one of the gmail.com sent lists/view works and the other doesn't suggests something might be wrong with the 1st 'location' format. I've not touched either for as long as I can remember. Could the upgrade have diddled the 'location' in such a way as to cause this behaviour or also duplicated a subtly different gmail.com 'Sent' folder? The main Tools > Account Settings does not appear to have a field that directly specified any of the 'Inbox' or 'Sent' Location fields that I can see; it just list my 2 email accounts, with my now broken gmail.com one listed first, with server settings - - Type: IMAP mail server - Server Name: imap.gmail.com - User Name: [email protected] - Port: 993 - Connection security: SSL/TLS - Authentication method: OAuth2 Can anyone explain where the subtly different 'Sent' gmail entries might have come from and whether either of the 'Location' fields look invalid? Also, since my gmail Inbox 'Location' looks to have a similar format of that of the broken 'Sent' item/folder, does anyone know whether it is invalid and can be fixed with a different location field?