Possible automatic signal bug

[spaceman-spiff]

I don't know if this is a known bug, but I placed normal signals here, trains arrive from two directions
When my first train passed, TTD changed the signals into pre-signals
But not all for, the left double signal hasn't changed

[Prof. Frink]

What's the next signal down each of the tracks leading off the bottom left?

[mnorman]

To clarify.
If the next signal on the bottom left is a one way signal, then this is normal automatic pre-signals, and all you have to do is return them to being standard signals and they will stay as such (at least until you change their direction)

[spaceman-spiff]

A double signal, there is room for a whole train
If I change it to a single, the automatic signal doesn't appear

[jfs]

With the signal set-up you have, it's actually perfectly correct behaviour. (And in the situation you seem to have there, I'd prefer to have presignals at that location anyway.)
Remember that changing the double-signals to single-signals will force trains to always take the seemingly shorter route instead of the first free.