Arnold,
I missed out that it was a siding shoe problem. My cars may not be post-war since all of them have the electro-mechanical plungers in the middle of the bottom of the car. I bought most of them at one time 5 or 6 years ago. Since I had HO trains from the time I bought my first set at age 12 until 2012 when I switched to O gauge 3-rail, all of the operating accessories and control was new to me. I can see exactly what you are saying about running fast on less than smooth trackwork would cause the sliding shoe to catch. I always had trouble with trackwork in HO and even now. I can't say I was all thumbs, but I could never be considered a craftsman either. No matter how much effort I put into some things, I am less than happy with the results. O gauge track and wheels are much more forgiving than HO; a definite plus as my limited dexterity deteriorates. Run them at whatever speed satisfies the modeler. 
