Capt. hardcore, check the top of the keg seal and inspect for any damage. Sometimes the seal can have a tear, cut, or crack which can cause the pressure to flow into the beer stream as it comes out of the keg. Also, check for pressure leaks and all hardware for any obstructions which could cause breakout.
As to the
checkball (102-527) in the coupler, this has nothing to do with pressure.
Scott Zuhse, Instructor
Micro Matic Dispense Institute