I did ran into the same problem while making the Road Atlanta campaign. I think it's better to use an official .lua file and modify it to your needs (at least if worked for me, and it will probably resist better to the updates). For example, take the levels\west_coast_usa\scenarios\derby_asphalt.lua file and modify the variables to make it work for your case. I think the names are pretty self-explanatory so you will be able to figure out what to change. But of course I'll do my best to fix it if it still doesn't work A problem I had ran into was the game not linking the waypoints to the AI decal roads, so If none of the cars are running you can try to change the waypoints field of the AI to the names of the waypoints on the DecalRoads instead (which you can bring up with the AI app)
