You know, as I delve "deeper into the internet" looking for people's experience with these locomotives, I'm starting to wonder if the two magnetraction magnets might be the problem.
I've now read two seperate reports of people removing the second magnet and the locomotive running much better.
I will say this - this thing has some powerful magnetration. I recently moved into a new house, so the trains are just running on some tube track laid on the floor. The first time I lifted this locomotive off the track, it took about half the oval of track with it! This might have something to do with the "excessive chassis drag".