I've noticed mine is real susceptible to any amount of dust on the metal platform. If I experience the sticking, I can ordinarily correct it real easily by cleaning the metal platform and the bottoms of the wheels on the forklift.
I'll also caution against using wax on the metal platform, a mistake I only needed to make once. The forklift hit the wood stack on the flatcar going so fast I swear to God the wood flew 6 feet.
Curt