That engine is from the late "last gasp" of N Scale brass. The Key/Samhongsa stuff got really good then, with coreless motors and finer detail than the brass had, say, in the 1990s and earlier. Look at Spookshow's reviews of other Key/Samhongsa steam from 2001 and later, and notice the trend of high scores and good performance.
The intermittent stalling is very common because the spring wire drawbar connection used on brass steam. Spookshow even mentions this in his review of this engine. But a hard-wiring across the drawbar will take care of that.
As for the 15" radius, I really must protest. Good brass engines are made so the parts fit with close, more in-scale tolerances, so they look more prototypical. And that means no more cheating and pretending a huge steam loco like this could run on anything like a scale 15" radius in real life. I don't think it's even fair to knock the engine for requiring at least a 15" radius curve.
