Given Rapid Transit is pretty much abandoned, I doubt shouting "high priority bug" will garner much attention. Does sound like a traction lock ergo user error.
It's been broken since TSW3 launched, the traction lock on the Rapid Transit Dostos doesn't come off in TSW3. I've reported it and moaned about it several times. DTG said it was known about, but there hasn't been an update. The traction lock will never come off despite doing all the correct things. A work around for the Rapid Transit Services is to select the Cab Car from another DLC, but the tutorial can never be completed (Except in TSW2 where it works fine). OP is correct, should have been fixed months ago, if you didn't have any other DLCs with a Cab Car, then you can't play any of the services that require it.
I don't remember if it was this exact tutorial, but I recall completing a cab car tutorial by driving the locomotive in reverse. Cab car wouldn't work, so I turned it off, boarded the loco at the back, and drove backwards using the external camera. Careful to open the doors on "the other side", but other than that, no big issue.
I must have been chasing an achievement. The only times I look for crazy workarounds for TSW bugs. Like this one.
You must be new here. Welcome! https://forums.dovetailgames.com/search/40259200/?q=Rapid+Transit+Dosto&o=relevance&c[node]=80
