Why do some signals stay red for no apparent reason?

[JonMyrlennBailey]

I have signals on the east end of the Mojave yard that stay red when no trains are even on the opposite side of the junction block. What can be done to troubleshoot this?

Should I remove troublesome signals? They seem to hold AI trains up for no logical reason.

I have also heard of this funny notion called "invisible trains" and they can hold up visible trains.

Can these annoying pests be eliminated from routes entirely if they are culprits?

Can consists even sitting in yards without engines or drivers control signals and lock junctions?

 

[stagecoach]

A wagon on the track is an obstruction so the signal will see that and show red. If the wagon is very near the junction (within the junction radius) it can block the junction from switching. All signals need to see the next signal on the selected path or else it shows red, that is why buffers are set up as a signal so on dead end track there is a signal for the approaching signal to see. If a train enters a yard track with no signals on that piece of track but a junction at the other end, the signal will need to see beyond that junction. So if it is set against the exit of a train the approach signal will show red.

 

[JonMyrlennBailey]

A wagon? A rail car?