Props Disappearing/False Ban

Do you still see props disappearing even after adding them to Objects AI Resource Whitelist (check here how to use objects-ai properly or it will not work) and Anti Attach Entity To Player Models White List? Then the issue is related to Block Pickups Spawn (in Pickups category) disable this option.

Also check if the vehicle is not among the blacklisted vehicles in the Blacklist category in Blacklisted Vehicles