[15.20] Rail signal not splitting valid block

[Finnboghi]

I was using robots to build rail signals along a long stretch of heavily used track to allow multiple trains to travel at the same time.

When one of the signals was built, it was cycling colours the way it does when there's an open loop in the network and it can't divide the line - except that there are closed blocks on either end.

I added more signals on either side, and they work as expected, with the block between them crossing the broken signal.

Removing and replacing the broken signal (manually and with robots) worked fine, and I haven't been able to reproduce it.

I was able to confirm that the bug survived a save/load, so I've attached the broken save here.

[Loewchen]

That signal is clearly not connected to any rail. NaB.

[Finnboghi]

Oops, good call!

I guess the bug should instead be that robots can place rail signals in invalid locations?