I got the opportunity to get into the basement this evening, and, of course, I needed to clean the track again, since several days had passed since I last ran a train. I didn't notice it at first, but a shiny spot on the rail caught my eye after I moved a locomotive. A closer inspection revealed eight shiny spots where a B23-7 had been parked. I could see how the rails around these spots were dull. Clearly, something is being deposited onto the rails, and the wheels kept the deposit from settling on the rails in those eight spots. I unplugged the dehumidifier in the layout room. We'll see if that makes a difference.
Thanks, guys!
DFF