Corny Keg making a chugging noise and foaming

Brewing Processes
1

I have a keg acting strangely.  It is carbonated and at serving pressure.  When I go to pour a beer it pours normal for the first ounce and then makes a chugging type noise and foams.  As the head pressure in the keg drops it eventually starts pouring normal.  When pressure is reapplied it starts behaving badly again.

To be clear the rest of the draft system and faucet behave normally with the other kegs on tap.  When I swap the faucet I still get foam.  It is a keg issue.

Anyone encounter this before?

2

Is it a dry-hopped beer in there? Could be hop blockage.

3

The only time that’s ever happened to me was with a floating dip tube that was tangled up

4

Likely poppet valve issue.
Inspect and clean poppet valves of foreign material.
I have found lint from my blue towels stuck in valves causing malfunction.
If no debrie then replace valves.