Vehicle Warehouse payout

No damage has been done to said cars, and I have made sure every time I am selling them to the specialist buyer for the 200k (I have GTA +) profit. This works fine when selling individual vehicles, but getting friends to help me sell more than two at a time results in me getting the money for only one car. Once delivered the game tells me I only receive 300k (public lobby) when selling more than 1 car. Help?