Comment 139 for bug 633352

I am experiencing this issue also, when syncing with a Horde calendar. I had the issue in TB 45.8 and also now in TB 52 with the Lightning 5.4b4 version add-in. Past reminders pop up, which is fine, but the dismiss and dismiss all do not work and result in the "the item has been changed on the server. Submitting your changes will overwrite the changes made on the server." Selecting either option to this prompt never dismisses the alarm, and the next time TB is opened, the reminders pop up again. Happy to provide more info or test. No one else is shared or invited on my events. My events were imported from an outlook .ics file (and all fields seemed to have imported correctly)directly into Horde. And then a calendar was set up in TB, and the events synced. The events with reminders in Horde are synced correctly and have the correct reminder times set in them. TB reminder date/times are correct; the reminders just can't be dismissed and keep recurring.