Mac Calendar.app freezes on trying to edit events

On the latest Sequoia 15.2, M1 Macbook Pro. Started happening yesterday. Any attempt to edit the body of an event causes a 1-2 minute freeze of the Calendar app, rendering it completely non-reactive/unusable in the moment when I place the cursor in any of the event fields. During the freeze, 1 CPU core seems to run at 100%.

Happens both on iCloud and on Exchange calendars.

On another Mac, configured with the same accounts and same MacOS version, no such problem.

I tried

• force-quitting and restarting the calendar (also with Shift)
• restarting the whole Mac
• disabling/re-enabling the respective calendars on the iCloud and Exchange internet accounts.

Any idea how to debug this problem? The Calendar is a life-critical app for me...