Yeah that solved the issue. Thanks for the help.

Ok Steam version was likely the problem.
For some reason Steam failed to update itself. So have made a complete reinstall.

Ever sins 2.1.15 (I think) the game complains about not being able to initialize SteamAPI and recommends to restart Steam.
Restarting Steam client does not help. And it is still an issue for me in 2.1.17.
This results in lots of achievements triggering again every time I load my save. And any BP not ...

I tore the stations down and rebuilt them. And now it works.
Wish there was a clearer way of seeing what wire is connected to what.

I might...
Check your circuit.
LTN correctly limits number of trains to limit trains.

Also having a problem...

Constant Combinator: (signal output)
train composition: position of wagons & locomotives in parked train (all stops)
binary encoded signal of train composition up to 31 carriages ...

I might just be making a stupid mistake.

I have the limit trains signal set on a constant combinator, connected with a green wire to the input (lamp) on the stations, for both the requester station and provider station to 1.
And still it keeps sending both my trains to the same places.

Which in ...