I do have the occasional short circuit. The original Wasatch UP passenger trucks have a glitch. Some of the early PSC Pullman and Harriman passenger trucks also have a glitch. A Lobaugh truck with a bent bolster will short. I have seen driver brake beam shorts on just about everything, and once in a while a side rod will touch an insulated rim, or a lead truck will touch a cylinder block. And the PSC CB&Q Hudson had tender trucks with shorts that I simply refused to tackle for any price.
This is not a problem for plastic models, so no wonder HO doesn't have short circuit problems. And if you run metal wheels on your freight cars, go with the plastic box Kadees. I pestered them for two decades, then somebody else got them to produce the metal coupler/plastic box couplers. Hope that guy gets them to do O Scale trucks some day.
Please do not repeat this post - it is copyrighted. Opinion.
So shorting issues are mainly confined to steam locos riding on curves too tight? HO & N model steam locos don't have plastic wheels or valve gear, but metal like O Scale; they don't seem to suffer like that. Still seems like a problem with the models rather than a problem with 2-Rail as an operating system. Certainly not a problem with diesels.
I use metal Kadee boxes on my rolling stock, on 36" radius curves at that. The trucks & wheels don't get close to them, and I fail to see how they'd short out anyway if they did?
Metal draft gear boxes are better than plastic in my opinion as they won't compress when tightly mounted to the underframe. Plastic boxes sometimes get squeezed and restrict or jam the free movement of the coupler.