Unity physics syncronization.

I'm working on a turn-based one vs one table game based on physics. Each player has checkers on the board. On your own turn, you can pull and release one checker to knock out as many enemy checkers as you can. Firstly I decided just to send the pulling position on each turn and everything went well till I add some obstacles on the board. Now it looks like each client calculates physics independently and gets different results. It is strange because in real-world if we would make two experiments with identical parameters we would get the same results. But in Unity, it doesn't work... Any ideas?