Not sure what happened to the other post, but below I've referenced a couple of threads from the last year mentioning this problem on two different loco designs. One of the threads has photos:
https://ogrforum.com/t...71#42820927485912771
https://ogrforum.com/t...05#42961695650136905
So the problem is NOT imaginary, or foundless bashing. If the wheels are worn down, slightly undersized relative to the design spec, or not pressed on straight the chassis might drag. Also, if the track is bent or the center rail is raised, the same phenomenon will occur. (In one of the threads, the poster mentioned that the loco worked fine on the test track at his local hobby store and only surfaced on his home layout.) If the problem occurs regularly, it would make the loco unusable.
Finally here's a prewar Lionel switcher of similar design. The paint loss on the underside of the gearbox suggests it contacted the track, probably the outside rails. I frequently browse the popular auction sites, and I've seen this evidence on other, more recent locos as well.
Thanks for viewing!
