Hot water pressure

You may have a buld up of crud. When was the last time you cleaned out your hot water tank. We clean ours about every 6 months. Remove the drain plug and run water through it. There is an attachment you can buy for this purpose. You will be amazed at the stuff that comes out. Arizona is the worst. Also if you have an electric anode it would be a good time to clean that but be careful you don't crack it. We use Wink to clean the anode.

Typically it is the hot outlet check valve (top fitting/line) that is plugging up.

The check valves are cheapo plastic junk that falls apart or clogs up.

With water off and pressure relieved you can remove the line then unscrew fitting on tank. You can replace with a nipple and install a shutoff valve vs installing another check valve.

No more faulty check valve just use the new shutoff valve when you bypass water heater for winterizing.

Your water heater has anti-reverse flow (check valves) on the input, output or both, depending on how your winterizing/bypass valve controls are plumbed. It sounds like one of them is getting clogged.

Sometimes it's necessary to remove/replace them. They will be located external to the tank (in the pipes) as they are installed by the coach builder and not furnished by the water heater manufacturer.