Traffic removes friends car

Hey guys, I’ve started my own private server to mess around with a buddy, and wanted to use traffic. However when I spawn them, my mate turns into a grey orb and I can’t see his car until I leave and re-join the server. Any way to stop this from happening, is it that the game tries to use his car in the traffic and removes it and just internally explodes or?? Really would be better if we can try to dodge through traffic at the same time!