It does it on flat ground as well.
I couldn't find zerk fittings, but i do notice that when i'm sitting on concrete driveway that the deck doesn't seem to go all the way down to lowest point possible. I'm betting there is something that isn't allowing the deck to move freely.
Given i have never done any maintenance/grease/etc on the deck that could also be playing a factor;
Pulled the dixie chopper book that came with and there really isn't anything that shows zerk fitting locations for deck. I'll keep looking but may end up trying grease the various places where i see chains, springs, etc. until i get a free moving deck.