When im playing with friends on a server, sometimes i can only see the standart model of the car they are in, it happens on specific vehicles like the Cherrier, ETK-800, Ibishu-BX, Brukel Bastion and so on, i cant remember when it started happening but it was there for a long long time,
Could you check if “Use simplified vehicles when available” is enabled in the multiplayer settings in-game? If it is, that’s most likely the cause of your issue. Please note that you will have to rejoin or respawn everyone for the setting to apply.