Simple answer, errant code, the same simple answer properly could apply for most bug's that call the game home too......
Specifically its when you select a timetable service and the time of spawning is after the service is scheduled to start. AI has already started driving it and you aren't permitted to take over (usually due to service moving too fast) and instead you are randomly dumped elsewhere Can also happen if you select a service of which the AI is still driving a consist that becomes that service eg. an AI train coming in from a portal and it is pulling into the station Can be circumvented by spawning in free roam instead at the location and near the time of the service you want (not possible for all)
