Has there been an earthquake or something on your map? Noa's Flood perhaps?
Well yes I have seen this before but this doesn't just happen randomly. It could have many causes. Have you by any chance played around with settings such as EngineSettings Terrain Z Bias, which is supposed to be at 50? All buildings and units are levelled for this setting of 50. Or maybe did you use any of the advanced map editing codes such as "addhi (amount)? Or maybe used the SurfaceGenerator and didnt set up the terrain to level at a global map height of 50? Perhaps unknowingly touched some hotkeys?
Does this happen on other maps aswell or is it only one map?
And when you say 'the buildings have sunk 'into the ground, do you mean you first placed buildings and then elevated terrain and as such they appear as they are 'sunk' in the surrounding terrain.
Or are we talking worse here and you mean when you take a squad over a hill it just walks trough the hill instead of walking over the top of the hill.
Perhaps show me the map to see if I can make anything off it.
And does this happen on NW or on BFE, Vanilla , patched, mod installed versions? Also, in your Data folder, are there any $$$temp$$$.xml to be seen? And just one more: in log.txt and loading.log, is there anything that isn't there normally?(besides the couple of sound errors and a few missing textures:my_pyro.tga)