I've done that too Brian. It works because eventually the AI will stumble on whatever was ailing them.
The other thing too is to ensure all the track spline points are yellow. Sometimes when connecting track, I've inadvertently miss-clicked and ended up with two track spline points over each other and not known they were not connected. When I went around the route, which was quite long with lots of crossovers and sidings, I found the two white circles. I clicked on them and only one turned yellow and the other stayed white. After a readjustment and a slide together of the two track spline points, all was good to go and I had happy AI at that point on.