Intermittent crankcase pressure issues

I should have clarified too, when you check blowby you look at how fast/hard the blowby is flowing out the hole in the valve cover. If it's spewing a ton like an old steam locomotive then you have issues, but if it's a small whisp of vapor that's completely normal. BUT even if that small whisp of vapor has nowhere to go it will pressurize the crankcase and cause the issues you're having.