Sometimes when reversing at a terminus, a train will reserve the tile closest to the end of the line -- and this reservation will not clear when it leaves the station, meaning that other trains are unable to enter that platform.
This bug is present in 11.9 and 11.23, but I had never seen it before I started experimenting with 20 meters-per-tile maps -- which makes me suspect that the map's scale is somehow role in this bug.
See the following save game/pak folder:
https://dl.dropboxusercontent.com/u/61716/reservationreverse.rar (https://dl.dropboxusercontent.com/u/61716/reservationreverse.rar)
Stay at Enfield Town. The train in the frame on loading will not demonstrate this bug. But the second one, which arrives shortly after, should do so upon its departure. This is easiest to see if you toggle reservation view with the 'B' key.
The reservation can of course be cleared by clicking on it, but it's not feasible to do this manually every time. Note that clearing the reservation will also clear the convoy in question's current reservation.
I use 125 m tile, and I have experienced a related issue - primarily with platforms at least twice the length of the stopping train, which will then become stuck (another train will arrive behind in the same platform and jam it).
I've seen that problem too, but only (I think) where choose signals are in play. I did raise it once before and I think the consensus was that the behaviour is quite deeply baked into the system and difficult to change. As a result I avoid choose signals at stations where this is in danger of happening.
The reservation bug, on the other hand, is a matter of a tile either being reserved in error, or a reservation remaining in error once the train has departed (depending on how you look at it).
I think that I have managed to find and fix this on the 11.x branch.