Greetings, I have had this problem with a recent 10 gallon batch of IPA that I dry hopped with pellets in the secondary. When I racked into the kegs, some of the hop particulate was also transferred. I thought this would settle into the trub at the bottom, boy was I wrong. In my experience, as it turns out, the ground hop particles plug the poppets, not the diptube. If your beer is carbonated, do not take off the poppets (duh right? I know, I have had stupider moments yet). Even if you bleed off the pressure, as I did, you can get a beer gusher. From the hop clogged tanks and one from when a teaball with hops popped open in a tank, I have found the best and easiest way is to rack to a new tank. Just let everything settle, bleed off the pressure through the valve in the top, open and rack over into a new keg. I had no flavor loss, no detectable oxidation, and no more stress.