For curiosities sake, Id like to see links to the 3 other forums that have riders claiming to have the same issue though. You said four forums in the video, and this does not appear to be one of them that has riders with the same issue.
I stand by my thought that something happened, more than likely NOT shoeis fault, to cause what you are seeing. It is just way too abnormal. Assuming all their helmets are made the exact same way, basically on an assembly line........ one would think an issue in materials would have shown at the very least across an entire lot of helmets. Not just one, or a handfull. I can see something that could have been fucked up in the assembly, like say a sheild mount coming loose or something, being an isolated or rare incident that the manu is at fault. But a complete failure of materials, in one..... or VERY VERY few of the helmets.
Something is amis here. Not blaming you directly. But something I think outside of shoeis fault has happened.
BUT WITH THAT SAID>...........
....... the way the distributor has acted is out of line, regardless of how you feel about what happened to your helmet.