I've got a couple of HO locos, some N scale locos and a number of HOn3 K-27s and in all scales and gauges I've had one or two locos that had issues. One thing I can tell you is that price is no longer an indication of quality. I spent close on $400 for an HOn3 loco and it doesn't run well at all. An HO Atlas that I paid well over $100 for sounds like a two stroke lawnmower engine. My DCC N scale Atlas loco arrived with a warped frame and I paid $174 for it. Changing scales will not make the problem go away. In the end, you have to make piece with the fact that no loco you buy will be perfect, each one will require some work, some more than others!
