It is only happening in the 1.7.2.5 patch, so too bad for all you dayz comander users who downloaded it automaticly. This info is just from what i have heard and experienced, but i play on a 2.4 server and our cars are always on the same spot when the server restarts. What to do about it i don't know, as far as i know there is no fix for it atm so just wait for a fix.