I have an 80s vintage 123R. I have two caps, both about 5 years old or more, both purchased the same time; one used regularly and the other held in reserve. Earlier this spring, the stove wouldn't make good pressure with either cap, showing flame at the base of filler cap. I ordered and received replacement washers from the Fettlebox and replaced both. The stove is now making good pressure with the pristine cap, but it still won't make good pressure with the heavily used one. Again, both have new washers. Still, the heavily used cap is leaking at the threads. I can also add that neither cap will produce a flame at the safety outlet even if I hold a lighter to it. The only flame I get from the cap is at the bottom of the threads. 1) Could this simply be a bad washer? (I have more at home not with me that I could try) 2) Can a cap deform or wear with use to the point that a replacement washer isn't enough? 3) Could a failing pip (not replaced yet) cause flames at the thread? 4) Any other possibilities I'm missing?