Hello HanE,
thats because they use some DLC's from ETS 2 like by scania is it the Mighty Griffin Tuning Pack https://store.steampowered.com/app/461244/Euro_Truck_Simulator_2__Mighty_Griffin_Tuning_Pack/
the problem is that TMP not can sync the DLC's to all the players and then you see something like that.. when you want to see the truck normal you have to buy it there is not a diferent way.. normal it's can be look like that:
The same can hapen by the DAF Tuning Packet https://store.steampowered.com/app/461249/Euro_Truck_Simulator_2__DAF_Tuning_Pack/
I hope i can help you