Thunderbird (Google) calendar entries disappearing

Intermittently, all events from (Google) calendars disappear from Thunderbird. The affected calendar is still listed in TB, but with no events.

Unsubscribing then re-subscribing to the affected calendar solves the problem, BUT it takes several minutes for TB to "find" calendars in the requested Google account.

Any suggestions for solving this?

Thunderbird 102.2.2 (64-bit) in Ubuntu 22.04 package. Not using any calendar addons for Google calendar. Other addons are CardBook, Emoji, & FileLink Provider for DropBox.