Fixing the Night

I've been the proud owner of an Emerald Night for over 9 years now. I love this thing to death, it's an absolutely beautiful build. That said, I have the same reproducible problem: the wheels jamming up. As the train goes about its movement, the piston crankshaft will slip from alignment with the forward wheel, causing the whole assembly to jam and requiring me to stop the train to reset it, only for it to happen again later on. I want to know how I can prevent this from happening anymore....