I think the KiHa 40 is a second generation chassis (iirc), but as you say with the original type of motor. These have the bogies held on by tension springs which pull them towards the chassis. The original chassis had compression springs to transmit the electricity from the bogies to the chassis. The problem was that the compression springs also pushed the gears on the driven axles away from the main drive gear on the chassis and out of mesh thus loosing drive!
So even with the same motor, the second generation design in the KiHa 40 is much better and should be capable of running well.
I don’t think any of the later designs are any better at running if the track is too dirty, people probably just don't show track cleaning because it's dull.