I was going to do that but try this test: place the cap with closed afc over mouth and finger plug the drip tip hole only then use finger to seal drip tip and seam. Former produces air, later does not. Seems to indicate the leak comes from the seam, as Tom said but I'm still confused, going to try different o-ring I don't have a tip that can seal the seam. Also tried tape over the seam with no effect.I think this points out the problem. I'm tempted to plane one of my caps by sanding it down to see if that does the trick.
So that's why my rm4 leaks like a sieveYou can sell clones on classifieds. Just can't sell counterfeit (1:1). If you remove all identifying marks you are good. If u notice Rob cuts the atomic afc down to remove markings to make It a rm4.