On Xbox some textures occasionally break, with something changing. (I don't know what it is, I've only had one texture issue and it's the Class 377 (ECW) cab going dark a couple of times, I don't know if it's that - or the compression of liveries, but it's something).
It's not just Class 377, it's all trains on all routes. In some it is more noticeable than in others. DTG needs to fix this with extreme urgency.