I can not be clear whether this is a TB/Lightning issue, or something with DavMail, but here it goes.
I have my TB configuration syncing with an Exchange calendar (and a Google calendar, which is a separate calendar and not an issue).
Earlier today, a repeating event was moved off of its day/time on Wednesday to Thursday. The event appeared properly on the calendar at 1:00 PM.
Later in the day, another meeting had its time changed to be 2:00 PM on Thursday. The second event appears now at 2:00PM, but the other event (at 1:00 PM) does not appear at all.
The event still exists on the server (the calendar appears correctly in Outlook).
The DavMail log doesn't show anything pertaining to the specific event.
The calendar is not cached or Read-Only in TB/Lightning.
First question: did you restart thunderbird to clear local cache ?
Did you check lightning logs ?
Unfortunately, I wasn't so diligent in reporting this bug. TB has since been restarted and the event does appear.
I will have a look for the logs to see if anything interesting shows.
Ok, closed then