I have a strange behaviour. I use caldav to sync my appointments from nextcloud to my mac calendar. There I can add a new appontment, but after that I cannot change it anymore. Not even delete it. Perhaps I drag the appointment to another day or time and after a few seconds it jumps back to the original place. Also when I delete it. It reappear within a few seconds.
I also use an android phone with DAVx2. And there everything works fine. I can move or delete a record and it stays as it is.
Has anybody an idea, what I can do?