I am having trouble setting up a couple of crossovers. There are two that seem to confuse Ai. The first is for an eastbound local to access a grain elevator on a westbound spur. I have the crossover set, then a section of track and then the switch for the spur. I have #6 LD signals at each side of the turnout. There is no signal for the switch into the spur. I have a track mark on the crossover track, just past the spur switch. But, Ai refuses to move. Eventually, nothing moves. I have something set up incorrectly, I'm not sure what that is. Help please.