Add 2nd tab - window is maximised to screen. Cant see tabs unless reduce window size

When I open a file to a full screen window for some tools it works ok. Open a second file with the same tool and it appears full screen. Clicking on icons etc on 2nd window does not work. If I make window so it is not full screen then I can see that I have two groupy tabs and now the icons work. Mouse click areas clearly do not match graphic underneath initially. I have this issue on outlook when I open a message to a new window as well as with other tools. Problem is likely linked to initial window being full screen.

First window (top left corner):

2nd window (top left corner):

Click on file menu an nothing happens. Click a little lower and it work - so mouse not aligned to image.

Move window to make it not full screen and I see two tabs.

And now the mouse clicks work as expected.