Troubleshoot: Try a single engine without cars and or a different one. Same? problem is the signaling of track. Works OK? problem is with the engine or somewhat applied brakes to cars (never see this before but you have to think on everything). Had this problem once. And the cause was a set of points inside of a tunnel, showing both red arrows. It got there by a gremlin in the program while I was modifying some yard tracks and they disappeared with points and everything (doing it in routes). Anyhow, because of these points, trains would run very very slow. Erasing this, and all is back to normal.
