Ran into a classic cornelius style keg issue this evening: I had just put a keg of my
Julius clone on tap this afternoon - the mate to the keg that just kicked from the same 10 gallon batch - and the first pour attempt was 50/50 foam/beer. As such defects just don't happen around here (anymore

) it definitely caught my attention.
The pour was smooth foam - no spitting - but I still suspected the root cause would be found under the Out dip tube flange. So I opened the keezer, popped the gas QD off the problem keg, latched the PRV open, then wrenched the Out post off and pulled the dip tube. This is what the O-ring under the flange looked like:
Looks pretty rough - there's a deep gouge on the inside around 7 o'clock, and a couple of inside dings around 5:30 all in the left picture, and a frayed perimeter around 4 o'clock in the right. I do not as a rule remove posts between keg fills so it's a bit of a mystery how all that happened - and why it hadn't caused issues before.
Anyway, I replaced the O-ring, sanitized the dip tube and post before applying them back to the keg, hooked gas and beer lines up, closed the keezer lid - and poured the below. Problem definitely solved
Cheers!