Originally Posted by Flybob
The tanks are a solid one piece when made. After they are installed the factory uses a hole saw to cut the opening where it is needed. Sometimes the disc that is cut out falls back into the tank instead of coming out in the hole saw. If that happens, it can occasionally block the hole. This could explain your problem. Over time, it should get stuck to the bottom or side of thank and be less of a problem.
Thanks Flybob, this makes perfect sense. I'll bring a wire hanger with me next time in the camper, and maybe I can snake it in there if it happens again. I'll have my service tech check it whenever I bring it in. I'm just glad it's not the B/W tank. ;-)