@StephanMenzelSAP this will be very difficult to track down without the code.
My uneducated guess is there’s some problem with the network authority setup of your class. Server correcting the client, but with wrong values.
I’m afraid I can only point you to some docs that might help you track down the issue (if you haven’t read through them already of course).
“Handling Client Error and Corrections” might give you some clues perhaps
Also check your network traffic with the Networking Insights tool:
Good luck!