Your Atwood uses one set of t-stats for both electric and propane operation
They are under the foam cover in outside compartment
Brown wires to/from normal t-stat (preset to OPEN at 140*F)
Red wires to/from ECO (high temp t-stat---preset to OPEN at 180*F)
If t-stats are not held tight against tank wall they can not properly sense the correct temp.
They are held against tank with a plastic washer that presses down a spring and then held down with three small tabs. I hate the design. (Suburban uses a bracket that screws down)
Problem is probably with the normal t-stat not tight against tank.