I remember a while ago (I think) that on Xbox, in service mode, the HST was limited to only a 6 coach consist, I can't remeber why. Why was this done and could it potentially be reversed?
This usually happens when you choose to stop at a station too short for the train. So check the length of the stations you stop at.
On gen 8 consoles (XB1 and PS4), the consists and timetables were limited due to the limitations of the consoles with memory usage. On gen 9 consoles, this limitation was lifted so both sets of consists can be used (it comes under the livery change feature) which adds more available services.
As Nick Y says it was done because on the last gen consoles, and the reason being having a large variety of stock assets messes up the memory, so they removed some of the different cars from the HST set to counter this. PS5 and new XB versions have the full consist available There is also a "hidden" version of the HST in GWR blue rather than green, but you'd have to search on how to unlock it and whether it's unlockable on console
