Let me describe this symptom and maybe you guys can give me direction...

[jeffy]

@MNWayne

I had a keg that would sporadically do the same.  I discovered a pinhole in the pickup tube.  When the beer level was above the hole, perfect pours.  When below, a small amount of CO2 was injected into the line causing foam.

I was going to suggest that this is the problem once Ken said he didn’t use a floating dip tube.