G71

I am currently seeing the same thing in gmoccapy if (and only if) the lathe macros are loaded.
The screen needs to be excessively large to see the tabs. (more than 1800 pixels wide)
But this is not a problem without the lathe macros (Or, possibly, it's the same with any custom tabs, I have not yet done that experiment)

I am trying to get the macros working with GTK3, so perhaps I will end up fixing this by accident.

forum.linuxcnc.org/41-guis/26550-lathe-macros?start=240#247195

I think that this issue might be fixed. The user tab and menus are now visible even is Gmoccapy is in a small window.
Resizing could still be rather better, but it does work (the content is created 4 pixels smaller than the window, then resized when the window resizes, making another 4 pixels available to shrink in to, and so on.