This may or may not apply, but it’s worth sharing. We have a Truma AquaGo water heater in our 2018 Oliver travel trailer. When we dewinterized this spring, it was only putting out warm water. The Truma tech asked when it was last decalcified, and because we are the second owners, I didn’t know if it had ever been done, and the unit did not have the original filter element. It had an upgrade that keeps the unit heated by electricity when driving, and it will not accept the decalc tablets.
I ordered and received the base filter & tablets, and ran the process. Much improved, but not at the expected temp. Searching the Oliver forum, I found a comment from another person who had a similar problem. It turned out to be the outside shower valves had been left on after winterization. Same for us. Valves off, we now have hot water
As I said, it may or may not apply to your camper, but it’s worth checking.