Dose it look like this cap. There is also a spot were the threads are notched out.
It also looks like the poppet is threaded in so it might be able to remove it and clean it up. Must be stopped up with dirt or something not allowing free air movement.
So why did you have to pay for it? Why wouldn't warranty cover that?
Can't answer that --- it's less than 2 years old so it seems like it ought to be covered by the basic warranty. I sent them that question. We'll see what they say. Thanks for bringing that up ----------
They may not like the hole you drilled in it.