The 666 runs great, but every so often it makes this guttural growling noise. Funny there is no sound decoder in it either. I tried to pick it up to investigate but it keeps growling, even when not on the track. I was told to send it in, but it won't stay in the box. The top of the box will suddenly fly off. There must be some kind of pressure differential I am not aware of. Consisting is a problem as well. It keeps trying to run over other locomotives. I can't explain it. Its like it has a mind of it's own or something. My priest says he might be able to fix it but I don't think he's well versed in DCC.