Not really, Neil. I sent a note to RSC when I found it was a consistent issue on the then-new Class 66 but received their usual vague and non-committal response. The GPU gadget made it clear that the memory usage increased slightly when the AI train finally appeared but you're still taking of a maximum around 650Mb out of 2Gb of dedicated GPU RAM so it isn't exactly short of space. It wasn't just my experience, either. Other users were reporting the same issue at the time. Nor was it one livery that didn't show. I can't remember if the trains involved used two or three liveries but it was more than one so it isn't an issue with a particular set of textures or the way they're built. The same liveries show up elsewhere in that scenario.
The one thing that it might be (though I don't have your route installed so can't compare) is that two AI trains pass the player within a short time but, thinking about it, there's another example on a scenario on the GW Main Line. I can't remember which this is but the player begins standing on a platform waiting to replace the driver who's brought the train thus far. During the wait, an HST runs into the adjacent platform but shows only as couplings. When it stops the train pops into view and stays in view while it loads passengers and departs.
To sum up, I know nuffin, Guv!
Keith
