Hello: I was lucky enough to acquire one of the Kato GS-4's when they first came out. Since it was a first run, I had to install the retrofit kit to install DCC. Unfortunately, afterwards the decoder didn't respond. Evidently, the retrofit wasn't applied right, although I could never figure out why. And eventually, after replacing the original board, the engine started acting very balky--wouldn't run if power was applied, or would do so very inconsistently. So I put it away for several years. Fast foward to now, and I figured I'd give it another look. I started by taking out the retrofit inserts, with plans to reinstall them later (but hopefully right this time.) Then I tested the engine. Still the same issues--on standard DC power, it either won't move, will do so with a large amount of jerking, or will run perfectly fine until it stops. I've ruled out dirty wheels as the problem--I cleaned them several times, and if the drivers are suspended in the air while power is applied to the tender, the drivers spin perfectly fine. I have had to fiddle with the drivers--all four sets popped out while trying to remove the inserts, and although I think I replaced them correctly, it's possible I didn't. I'm not totally sure what's going on here--could someone give some advice? Also on the inserts, I currently only have the two that I placed on the engine way back--not sure where the others are. Does anyone know if more are available somewhere, or could be crafted?