I rebuilt my 50 year old AS toilet with these valves 6 years ago.
Recently I installed a tankless water heater that includes a hot water recirculation using the cold water as a return.
Not the water is warm to hot at first when flushing and the valve will not fully close at full tank.

Did the recirculation cause the seals to fail on the valve?
Is there a fix? If I replace the valve again with a same design,
Will my problem return?

What are my options?

Thanks!

Did you repair the fill valve or the flush valve? And which is not closing properly?

Getting 6 years out of a fill valve is pretty good nowadays
It’s never a good thing to have hot water in a toilet
It will cause mildew and odor and could possibly contribute to replacing the wax ring often
Replace the fill valve seals or the entire fill valve itself

Thank you for your reply.
It’s the fill valve that is not closing when the tank is full.

Replace it with a Korky or Fluidmaster.

Netconcepts,

When you wrote:

"Not the water is warm to hot at first ...."

Did you mean to say:

"Now the water is warm to hot at first ...."?

Are you saying that the water supplying to the toilet is warm to hot and not only cold water or am I misunderstanding?

Your bypass valve not operating properly and is allowing hot water into the cold system. Hot water entering a "cold" toilet tank, or toilet bowl, can cause it to crack creating a flood.