Interesting. My Pride Lines Hiawatha runs great, but is top heavy and easy to flip.
I bought the O-31 set with knuckle couplers. Out of about 52 stamped wheels on the tender and cars, at least 35 of them were stamped wrong, with the inner and outer holes not lining up, and wobbled like crazy. The owner replaced them for me and I sent the wobbly ones back.