OK, after months of smoothless, flawless running on my portable indoor layout, tonight I started having track power problems. The locos sputter, stop, stall then race. I'm so frustrated. At first I thought it was a problem with my USA switched (the cheap little plastic ones). So I checked and tightened all the little wire contact screws. No change. I noticed that when I giggled the track, the train started. So, I tried screwing all the joints together around the switches. Better, but then it happened again in a curve away from the switch. I took the curves apart. Then I saw it. Black carbon dust in between the tracks inside the joiner. Is this the problem? I was planning on screwing the entire layout together at all the joiners, but I hesitate as this will make it much less portable and difficult to tear down. If the carbon dust is the problem, I can just clean out all the jointers and get back to flawless running. What does everyone think? Is this a common problem? Or, could it be something else? HELP!