Problem with setting Icon on Forum List

The picture below shows one of my subforums. After much comparison and troubleshooting I cannot figure out why subforums 3 through six have the wire-frame black and white icon, while the others have the blue circle icons (at the far left of each line). Can anyone suggest a setting I should explore or otherwise suggest a way to get these icons uniform? Thanks in adance!

woltlab.com/attachment/170588/

I think this thread got marked resolved because it was never answered. Can I ask the same question again this time with another picture, as i still have the same problem as before. This is the way this looks on Android:

This is the way this looks on a regular desktop with the default woltlab theme. (I tested it with the default theme just to be sure this is not a custom style issue):

I have pored over the four forums to see what might be wrong with them but I see nothing that distinguishes forums 3-6 from the forums that are looking correct (the first, second, seventh and eighth).

Can anyone suggest a course of attack? Thank you!