This happened to me a few times.
Just purge the relief valve a couple times,sedement(rust) builds up at valve.
Its usually when the electric heaters just turned on when it hasent been used for some time.
I sometimes purge the valve after I set up ,and then I never have a problem.
I dont think you should replace it,just purge it every once in while when its under presure as preventive maintainance.