make sure the pickle fork isn't bottoming out and not actually "wedging". is it the right size and i didn't know they could bend over time - but make sure it's working as it should.
1. Use a HEAVY hammer or larger solid metal mallet with lots of weight behind it.
2. SWING HARD.
light hammers and construction style hammering isn't the ticket here. This is more like "stand back, wear goggles, cover your ears, and scare the neighbors"