Sync problem with calendar after provider Update

I hope you can help me.
I can’t figure it out, if it is a server or a client problem.

I’ve been synchronizing my contacts and calendars with DAVdroid over years.
Now my provider Hetzner.de has updated the Horde software (Version unknown).

And now DAVdroid is reporting a error during the synchronization process.
He synchs my contacts, tasks, and my calender 2 and 3 perfectly and with no problems.
But my main Calendar1 reporting an error:

Server error while listing the server entries

Attached the debug info.
(Just removed my personal stuff)

Don’t know what this message is:
Expected 207 Multi-Status, got 200 OK

Thx for your help!

DEBUG: https://paste.fedoraproject.org/paste/YcetpcbXA1NHfFBFEu70KQ

rfc2822

This is a server problem. Please contact Horde support and provide your DAVdroid debug info.

I’ve fixed the problem.

The problem was caused by old calendar entries.
Clearing the howl calendar made the error disappeared.
So Thread could be closed.

Thx for your answer!