Got another checksum. Sorry to do the Phil but can you remove all the 'data' folders for the cars on the server.
I've got my server running and so far I have found all that is needed is:
server/content/cars/example_car_2 ;and so on for x amount of cars
So the checksum is done on surfaces.ini but none required for the cars unless a data.acd file is present.
Whether it's AC or sTracker, one of them seems to trip up on something if the car has a 'data' folder.
When there are data.acd files the checksum gets done first and you can't even connect to the server, unlike our troubles where the message comes up in red after we have connected.