Maybe I'm missing something on the water heater...

We have a Suburban heater and we have two switches in the trailer and one on the heater. One in the trailer is propane and the other two are electric. Both electric switches have to be on for ours to switch to electric. Check the propane side. It recovers faster than electric as well which may account for your more plentiful hot water. Also, if it is hot and you are sun side with the heater, it can heat up the water a little.