Thanks, got a step further now. Looks like a know issue Unreal Engine Issues and Bug Tracker (UE-144539)
Closing connection. Can’t send function ‘ServerUpdateState’ on ‘ChaosWheeledVehicleMovementComponent SportsCar_Pawn_C_0.VehicleMovementComp’: Reliable buffer overflow. FieldCache->FieldNetIndex: 4 Max 5. Ch MaxPacket: 1024.