I have two CalDAV calendars on my Synology Drive. Whenever the Synology drive is doing other tasks and Thunderbird is symultaneously trying to update the calendars, the following will consistently occur: 1) A small error next to the calendar will appear stating the calendar is momentarily unavailable. 2) If the Synology continues to be busy, the calendar will automatically disable and a button will appear next to the calendar to enable it. All appointments and tasks are removed from the calendar and task windows/tabs. If step 2 occurs, the calendar will not re-enable automatically. It will remain disabled until the user manually re-enables it. This risks tasks and appointments being missed. I regard this as a bug. A serious one. Is there a solution that I have not yet found despite looking everywhere?