Strange...

I wonder if the padding under the lining is glued up properly.

My head is officially Shoei shaped. I can buy any large Shoei helmet & it will fit comfortably without mods. Don't know whether that is lucky or unlucky...

I'd have a look at the padding by pulling the lining out & checking that's all is where it should be. There may be a fault with the workmanship.

The Hornet DS is a great helmet, it's worth persevering with, maybe even trying on another one at the shop.

Good luck, Boneman