2 decimals max, and ive had buildings thousands of studs away from spawn and their fine, the building this is happenign to is like less than 20 studs away from spawn
then try to test it on a completely new place like an empty baseplate and see if the same effect occurs to see if its something in your game or some other spooky thingy thing
i got no idea at all but im glad the problem is fixed… i dont know much about terrain since i dont build very often on it but i think you can mark this problem as solved with your own comment ^_^