Usually，if you want to play DLC vehicles， the best way to do is spawn them manually by trainer. If you want them automatically spawn on the street，it is ok but make sure related mod are the latest version and you installed everything correctly.
For example，I had IVPack installed before，they can spawn IV vehicles and some DLC vehicles on the street. But this mod is currently outdated，so if you install them and the vehicles spawn on the street crashed my game.
Now I can only spawn them with trainer and disable spawn on the street and wait until a new update is available.