Ok a lot of good info here. From what I have read testing the hot water heater like a a home unit (leaving it on) it not supposed to harm it as it cycles to keep water at a certain temp.
Now yes initially I would fire it up and leave it running. In a few the water would heat up to the temperature of molten lava. In a few hours it would lock out ( unit switch on/ switch light on / unit fire off water tepid. Now it has not gone into lockout but the water is not really getting hot as the unit shuts down prematurely .
The thermal tape on the Tstat & eco is shot & loose. I know the burner is clean & working as this the igniter.
It can only be the sensors or the control board. I will start with the sensors first as they are inexpensive
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