Low hot water pressure

[Freewill]

We're experiencing low hot water pressure. We've replaced the back-flow valve with no improvement.
What's odd about it is this.... sometimes we have normal pressure on the hot side but NO hot water no matter how long you let it run. We have then turned on the hot water at another facet and it will have low pressure with hot water. While the other facet continues to run normally but cool temp. Only when I turn the facet off then on again will it begin running hot at low pressure.
We also noticed when I run the hot water in the kitchen and the pressure is low, if I turn on BOTH the hot & cold in the bathroom the pressure improves in the kitchen.
This is so frustrating!

[sourdough]

How old is the trailer/water heater? What brand? When was the last time it was flushed? Have you checked the outside faucet/shower? Are you on city water or water pump?

[Canonman]

Have you checked the HW bypass valve?? Might be only partially turned back to normal. The WH will fill but would have limited pressure.