For anyone still following this or comes across this in the future. While waiting months for a replacement OPV, I found a fix that has been working very consistently for a few weeks now.
The indent from the spring on the green rubber valve seat in my machine was very off-center, meaning the spring was crooked when installed and not applying even pressure, likely causing the metal part of the seat to rub and catch on the inside of the housing. Other have suspected this to be a root cause as well.
So, I pulled the valve seat out, and using a sharp utility razor, I shaved the top of the valve seat off to create a new even surface. Basically reset the install. I was careful to reinstall and hopefully keep the spring better aligned.
My machine has been running very consistently since doing this. No more spikes and the pressure hasn’t starting creeping up again. For anyone with an uneven valve seat indentation, I would now recommend going straight to this solution along with a good lube while you’re at it.
