Axis moves when object is grouped

Hello fellow SketchUppers!

I have some problems with my axis. I drew a house foundation with lines parallell to the model axises. But when I group the foundation the axis moves! The foundation is no longer parallell with the object. What am I doing wrong? Can someone please help me? I added the file.


Building house.skp (11.4 MB)

This is what’s happening…

Draw the exact 90 degree angle