With moss in the hides the humidity level will be higher in them than in the rest of the cage. I still have a ball in a glass tank and moss in her hides and occasional misting gives her perfect sheds. I would honestly guess your humidity is much higher than you think and your equipment is saying.

I can't really tell from the pics but if the humidity gauge is near a light, rhp, or uth it could be giving you a low reading because the heat is zapping your humidity from that area.

What bothers me is a rheostat on a rhp. Those things can really heat up. Do you use a temp gun to see what the surface temp is under it?