Just a word of caution if you plan on checking for a blockage yourself-- leave the tank valves CLOSED! The gray water may not be to bad but that black water could get really messy if you have it open and remove the blockage!
I'd insist the dealer do the checking and let him get the mess!
Steve- that Ridgid scope is a must for us in the RV's. We could check alot of things with it without actually dropping the whole belly to see things or possible problems! I see everything on the unit but a price! Any idea on that? I checked to see who carries the units and I see Home Depot does and will check there!