I think Wiredsport might be on to it.
If your stance is really wide it can make buttering suddenly a lot harder on some boards cause of their flex pattern. At home, try out a skinnier stance and see if it's easier to press.
I'm 145lbs. and I prefer 152cm for riding around the mountain, but still being able to lay a press easily. If I make my stance too wide(which is a bit more natural feel to me as I have very long legs being 6ft tall) it makes it much harder to get leverage over the board.