left mouse click expands window

I am using windows 11 and occassionally the left mouse click causes an Igor window to meaximize in the vertical direction.  This happens when clicking on the top bar for example to drag the window.  Using the Esc key returns the window to its previous size.  Once this behaviour has started it continues until the experiment is closed.

Has anyone notice this and have a solution?

Which Igor version you are using? You could also try to copy in the latest nightly build (Help => Nightly Builds) and see if the problem goes away. Do this at your own risk, though.

P.S.: I am not using Win 11 and try to avoid it as much as possible. So no confirmation from my side.

Do you have some sort of Package installed that manages a desktop, or adds some automatic behavior to Igor? I use Windows 11 and have never seen such behavior inside of Igor.