I'm having problems with Thunderbird because Lightning is deleting events. The problem has been going on for several months. Since March 2021 I've been making backups of the file "local.sqlite" and writing down exactly which event was deleted on which day. As a rule, deleted are the events for about the next two weeks and about the previous week. A gruop of events are always deleted at once. I cannot say in advance when this day of deletion will be. Therefore I cannot reproduce the problem. Both one-time and repeated events are affected. If I have entered a birthday event for the next week, then this event and all events from the following years will be deleted. It doesn't matter what I do with the event in the reminder window before the deletion (close or postpone or nothing). I'm using the latest version of Thunderbird Portable (78.9.1 64-bit). The following deletion days have occurred since March: Day of deletion: 2021-03-01 Event: 1. March Event: 1. March Event: 1. March Event: 1. March Event: 5. March Day of deletion: 2021-03-23 Event: 19. March Event: 20. March Event: 23. March Event: 26. March Event: 27. March Event: 29. March Day of deletion: 2021-04-03 Event: 18. March Event: 24. March Event: 1. April Event: 1. April Event: 2. April Event: 6. April Day of deletion: 2021-04-13 Event: 1. April Event: 8. April Event: 10. April Event: 12. April Event: 16. April Event: 17. April Event: 17. April I found this page in the forum: https://support.cdn.mozilla.net/de/questions/1326232 The same problem is described here. It is claimed that the latest version fixes the problem. But that's not true. The title of that page sounds like a problem with the reminder. But the reminder works right: There are noch events to remind. Unfortunately I cannot answer there because my Firefox account is not accepted. I get the message: "This account is not active." Please help. I know one other person with the same problem.