atlantex,
Each ArchiCAD element has a unique ID that identifies it, and there is a map that records which elements are linked to other elements. There could be a problem with the element unique ID of the window, and therefore it is mapped to the wrong wall.
Please send the file as a PLA (so it contains the library parts) to your local ArchiCAD representative, who will send it to Graphisoft for investigation.
Thanks,
Greg
Gergely Kmethy
VP, Customer Success, Graphisoft