There was approximately one or two hours left till next server restart.
We pitched the tent, then there were several server restarts the next two or three days (server with 6h restart duration), and everything is still fine.
But at the fourth or fifth day (we haven't played for just one or two days on this server), all of our four tents were packed at the same places we pitched them.

I know, but it's enabled on this server. As I said they only get packed after few days.

Hello,
the game does not crash with an error message. The whole PC completely freezes and has to be resetted by holding the power button for five seconds. No error message occurs.

well, did you use the steam start parameter -newui? if so try to clear your steam start parameters.