@KorNoob Thanks for sending the package. Please note that we requested a minimal Unity project which still demonstrates this issue, but your project and example scene contains a network manager with all kinds of unrelated things. Please understand that we don't have the time to debug your net-code for potential issues there.
You need to boil down the issue to a reproduction scene which just uses one or two scripts which re-create the whole problem, with as few lines of code as possible, definitely without any network code involved. Then we can have a look at what's going wrong.