[Duglas]

I recently purchased a Valken Proton off a friend who'd used it twice.
Worked like a charm for a few months and then the last time I chronoed on my field, the air starting leaking out the grip.
I've now had this issue for a few days.

I have tried:
Taking apart the entire grip
Lubed everything manually
reseated the regulator and stem
reseated the ASA

the air is coming out of the hole above the bottom grip cover hole.

My local shop says it's stem related and I need to order a new one.

Anyone else have this problem and fixed it without buying a new stem? or is it a different issue and not stem related?