Thanks for the inquiry!
I would certainly say the Check Valve is typically the culprit when this happens so you were right in replacing it. Typically if it doesn't seal up when the unit shuts off all of the tank pressure will put back pressure on the pump and can cause this to happen.

I would make sure you have no debris in the head, lines and in the check valve, which will cause it not to seal/seat.

Otherwise, just make sure the Unloader Valve on the pressure switch is "blowing off" or unloading the excess air in the line after the unit shuts off. If it's not unloading after shut off you'll have that excess air pushing itself against the pump as well.

Hope this helps as a starting point.
- MTR

Great, glad you've found the culprit! I did forget to mention this one fact, that it could be the oil breather is not "breathing" or venting which will cause too much pressure to build in the crankcase. Sometimes it's that simple.
Good luck and thanks again for the question.
- MTR