Upon the login page of the game, you should put a notice that states:
"If you don't have the Heavy Haul DLC, that type of cargo you will see on the road will appear as a 'blank/empty trailer' and you might see banners/flags missing."
Users are also stating in the Discord that banners/flags on the trucks either. Just some more added info.
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Issues:
Issue 1) Beacons, flags and banners don't show for DLC players.
Issue 2) Sometimes the end of the trailer disappears ( https://vid.me/Thar ) and goes under the map?