I have 2 check valves on my Journey. One in the hot water line coming out of the water heater. The 2nd is in the line from city water connection. The line splits. One side furnishing the cold water. The other line goes to the water heater and has a check valve just after the split. I have had both of mine go bad at different times causing me to have no hot water.
Call Winnebago. The tech will be able to look at the plumbing diagrams and tell if you have more that the one. Finding the second one was a pain in the but.