I have an Athearn AC44 and am having trouble getting it to run smoothly. At times, pairs of drivers will bind up and not turn at all as the other push them along the rails. I've tried some bushing break-in fluid followed by a flush and re-lube. I'm pretty new to the hobby - is there a tried and true method? Do you get a lemon once and a while? I have a few Katos and Proto 2Ks on the track and they totally put the athearns to shame - Advice?