Birthday calender / caldav sync issue


i have a nextcloud instance with several calendars. My birthday calendar shows this error for every single entry… all the time. I can ignore it, it pops up again, I can delete it but that can’t be the solution?

Any hint to debug this?

2022-11-29 10_49_33-eM Client

also emClient assigns one of my calendars to the task feature which is clearly not right… ?!