East Coast USA on Xbox Series X version 1.0.11.0 of the game. Having a vehicle on board an Aircraft reduces the Squad capacity by two for deployment missions. The particular aircraft capacity is still six, allowing the vehicle (which takes up three slots) to be carried with an additional three soldiers. However, once in the ready screen, that vehicle cannot be deployed with those soldiers as it simultaneously reduces the squad size and takes up three squad slots itself. It looks like some improper values are being used to calculate the various capacities. The net effect is that vehicles are essentially unusable in game due to this doubled penalty.