A ghost?

Today I played again with my model railway.
If you want multiple trains to run at the same time you have to ensure that they don't run into each other. There are a number of ways to do this. (The latest international standard demands that the trains report their position continuously radio based. Most model railway owners are not ready for that yet.)
One of the ways is to split the complete set of tracks into blocks. Block occupancy detectors notice that a train is in the block and pass this information, together with details about the train, to a controller.
Usually a computer program listens and talks to the controller and interfaces with the user.
To make a long story short: my test track had two locomotives, but for some reason the system reported a ghost train in block1. Although this part was definitely empty. And on both sides of the block the railway track was separated from the rest, as it should be.
Weird. I guess I will have to spend some time on this. It's all new to me.