I just pressure-tested another keg I have that looks like it's been knocked around a bit. It holds pressure fine to 20psi, but above that there's a faint "hiss". I replaced the O'rings for the lid, dip tubes, and put new poppits in the posts. With a a little soapy water I noticed that the leak is actually coming from a worn section of rubber near the "IN" post. Is there a way to seal this up? It's very faint...it takes maybe 5-10seconds to form a soapy bubble that will pop. Nonetheless, I don't want my beer going flat.