:ditto:Unless the oil is overfilled or the engine operated on a steep angle, I would suspect blowby. If it is blowby, worn rings or stuck rings would be the usual culprits, other symptoms would be oil consumption, oil on plug, or frequently fouled plug. I personally have not had a valve issue cause oil to be pushed out the pcv, but I can't say that I have seen it all. Good luck.
I suspect steep angle such as mowing roadside slopes.