macos – Screenshot of an X11 box gets white

I’m facing a little problem while taking a screenshot of an X11 window
(using XQuartz – if there’s something better out there, lemme know).

I tried everything:

  • Entire Screen
  • Window-Only
  • Selection

Even tried recording the screen, same results – the box I need to screenshot (the one on the right) is always white:

enter image description here

(Side note: In the pic above the window is not “focused” (selected), but even with the “focus” on it, nothing change – even tried using the XQuartz setting where it focus the window on mouseover.)

This is how it should be:

enter image description here

Any idea on what setting I might need to change, in order to get my screenshot to work properly?

Oh… Almost forgot, I’m running the last macOS Catalina update (10.15.6)

Thanks in advance.

Edit: Added a pic of how it should be.