So we have a large assembly consisting of four main blocks. For some odd reason, some of the walls show up in a drawing as if they would be envelopes -- while they most certainly are not. It happens on all of our computers. We have gone through all possible settings, configurations and display states that we can think of to figure out what might be wrong, and haven't found anything. In individual subassembly drawings those walls appear just fine.

This is the first time any of us has encountered anything like this. Any idea of what might be causing this?