Compared to for example, Siege units which also feature these load carrying wagons, Mongol’s packed wagons are devoid of sound and animation, with the exception of their wheels turning.
The packed wagons even feature a small flag, is frozen in time, and faces against the wind in that stance.
Siege units also feature animation other than just their wheels, like in this example that is missing from Mongol wagons.
The total lack of sound does not seem right either. I can only assume that the wagons are currently bugged.