Thanks for the input. This time out, we are using an ample amount of flush water as suggested; we will se what the effects are when we dump this time.
Historically, I have always flushed the black tank first and run it out of liquid and solids, as viewed through the clear elbow. Then I close the black valve and drain my 2 Grey tanks as I refill the black tank via the San T Flush valve. Finally, I re dump the black until she runs clear. I might even have to keep the San T Flush running to achieve that. Before I disconnect my sewer hose from the dump connect, I flush it with fresh water. This has worked well until the last 2 times out.