I have not your model here, but from my experience with it, I would say it is a mixture of the belt-progress (the map) and the strength of the wind (I would see here the prime effect, but yes, that depends on other parameters, how much the cloth resist the wind, e.g., Tear).
Please have a look to the link below, please note that I Used only the Inverse map!
All the best
Hi John Liebler,
Sorry about that, I have no access to any option to solve this from here, but I have set up a scene file and linked it below. I hope that helps.
My best wishes
Scene file (this will be here until the tutorial has a file to download.) Please note that I have set up here only a dummy. I used as well a friction field here. I found that using one map only might do the trick. Both maps are included, so feel free to drag them in the fields according to the tutorial.
Scene file including Cloth Cache