@Punisher666 The best way to prevent all of the problems related to having multiple Add-On DLC's is to create your own Add-On pack on which you install the vehicles that you want in an specific order and carefully. I don't recommend at all installing Add-On packs created by other people that's not yourself.
I've been the last 2 years installing/removing vehicles that I wanted/got tired on a single DLC pack created by me and 0 problems.