Game version 5.2
When the truck move/twist the light don't follow properly the cabin parent frame.
Ive had some interesting glitches with the roof light bar on that truck. If you go into deep water with the twin snorkels attached, the light bar tweaks out and flinches all over the place. My glitch is in the main game, not the PTS. I know this is the PTS section, but my experience is relevant to the OP.