Desync without mods

[synt]

Hello together,

I have started a dedicated server at a server provider. We started a map without mods and played the last days.
Now everytime, when one of our mates is joined nobody can do anything...
We can run around and open menus, but if we do something like build or erase some buildings or try to load blueprints from the blueprint storage, then the server response with desync alert and that´s everytime.
It is unplay able. We tried to start the save at my local pc and after he joined, everything is working fine.
Then I reinstalled the server and copy the savegame to it, same scenario... nothing is working fine.

We do not get it whats wrong or what happen here...

I uploaded the desync report, maybe one could help us?

PS:
Honestly couldn´t upload the desync report here, got error "413 Request Entity Too Large"
so here is also a link:
desync.rar