Dark Guild menu after Guild Wars

Platform, device version and operating system:
Steam, Windows 7 x64

Screenshot or image:

What you were expecting to happen, and what actually happened:
After playing my Guild Wars battles, when I exit the Guild Wars screen, the Guild Wars menu screen (shown above) is darker than usual. Actually, I just checked and it’s missing its usual background image. Functionality does not appear to be affected.

How often does this happen? When did it begin happening?
This happened every day during the last Guild Wars (June 2019), but only after playing the day’s battles. (I didn’t try it after playing less than my full quota of 5 for the day.) I believe it also happened every time during the previous Guild Wars, and possibly the one before that. However, I seem to remember it wasn’t as consistent prior to the last two; maybe I just hadn’t twigged on that it was always after playing battles.

Steps to make it happen again
See previous.