Are you sure you are not rotating the 3D preview so you can see the changes to your object?
This will rotate the plan view as well (I often fall for that!).
Having said that I have had the situation where an object rotates 45° in the preview and no matter how I try to rotate it more I can not get it back to being square.
It hasn't happened often and I can't remember now if the rotation angle was showing the correct angle or not.
I can't even remember which version this has happened in (I work with many).
It is one of these 'can never make it happen unless you don't want it to' things so I have not been able to reported it as a bug.
Make sure you have the latest hotfix (upgrade) for Archicad.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11