BUG: google calendar invites not syncing

I got invited on google calendar event.

Event is shown in Morgen → I click to edit event, RSVP, accept.

This leads to “! Morgen could not sync your latest changes, please retry” message on the event. Clicking RETRY does not help.

Hitting Resync does not help.

The only option currently is to go to google web calendar and accept the invitation there.