Mixer on secondary screen

If I put the mixer on the secondary screen and maximise the window, if I press F3 to hide it and then F3 to reopen it ends up under the project window.
This happen if I open a new project too.
This happy also if the mixer window touch a border of the monitor.
If the mixer window is not maximised (and doesn’t touch any border) it work like aspected.
Thank in advance for your help.