Years ago I experienced the fact that glass thickness is not constant in all Doors/Windows in the Archicad library. Some of them have a cetain thickness, but some of them are are just a simple plane.
The scale and the 3d detail level settings also play a part. For example, if a 3D is at 1:200 or higher, the model will be wrong and a single plane of glass will float behind the mullions. Wrong plan, wrong 3D.
For 3D, always set the scale to 1:100 or 1:50. No view related level of detail for the objects, and they are definitely not scripted to change the detail level based on the distance from the camera by default ...
I suspect that the combination of single/double pane glass and material assignement is the culprit here ...
ArchiCAD since 4.55 ... 1995