The beer might still be over carbonated from when it was on the bad regulator. Venting the pressure a few times may not have been enough to degas the beer, depending on how long it was exposed to 50-60psi.
Alternatively, it could be an issue with the lines as has already been suggested. Too short of lines, etc.
What kind of setup are you running? Cobra/picnic tap? Tower tap? Coffin box? Collar keezer? Holes in the side of a fridge? Kind of hard to diagnose the problem without knowing more details.
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