Have only played electric so far - another Steam user brought this up.
Assets\G-TraX\Preservation\RailVehicles\Steam\Northern\Default\Tender\GX_Loco01T.GeoPcDx is referring to the wrong texture folders and not using the supplied ones. For many this results in Missing Texture error.
As I will not distribute any GeoPcDx files, I have described how to fix it successfully on the steam forums.
https://steamcommunity.com/app/24010/di ... 506901867/