Just as a suggestion I would put that fill water to work. Add to your toilet some water, some water softener (Calgon), ice cubes and laundry soap, hook on your tow vehicle and go for a drive with lots of corners to clean out the inside. Toilet paper maybe covering the sensors in your black tank and this cleaning may dislodge that paper. After dumping everything I would add some bleach to all the traps. It's a dirty job but somebody has to do it!