Noticed that my BB was not running smoothly under speed step 17 - crawl speed; it was moving hesitantly. So, took a shot in the dark, and replaced the cap with a new one and used one suggested by GRJ. See pics; I had originally used one I ordered from Lionel; replaced it with one suggested by GRJ; now it is back to running real smoooooth at crawl speed. Possibly I did a bad job of soldering on the original one; did better on the replacement.
Here is the GRJ replacement one Nichicon CAP ALUM 4.7UF 20% 50V RADIAL, 28 cents each.