I'm running Thunderbird on Arch Linux. A few weeks ago the following problem appeared. When I start Thunderbird I can view my calendar as usual, and it is all in place. But once I click off the calendar back to email, any attempt to return to the calendar shows it blank until I restart Thunderbird. My various calendars are listed, but all appear empty, and Tasks are similarly empty. When on my email, the Tasks bar is still working.

I can see a similar question on the forum, to which the solution was to delete calendar add-ons. I have tbSync and its dependency installed; I tried deleting them (by moving the relevant folders out of .thunderbird and restarting) and this did not help. I have also tried reinstalling Thunderbird, which also did not help.