Buildings collasping
 

Italy vs Green, 1973 Fight in Rome. A large warehouse/office like building is hit with HE rounds in the center hex of the side facing towards the top of the building. The resulting damage causes the part of the building to the left to collapse as well. This in turn causes the whole building icon to collapse and disappear, no rubble nothing but open space where the rest of the building was. The on rough and rubble are showing is the location of where the first HE round hit and the location to the left of that.

The building filled 3 hexes by 3 hexes. The funny thing was I had just wonder how or what would it take, to cause a whole large building to collapse. Well, now I know. LOL.

Update. The building ICON vanished form the school, the game is still treating those spaces as if the building was still there.

Re: Buildings collasping
 

Try restarting your game and I suspect you will see the rubble. What you describe can happen on occasion where the game gets lost but normally it straighens out after a restart or reboot