I was having a problem with the antifog visor on my Bell Sprint helmet. It is a Bell antifog replacement visor made for my helmet, costs about $35, and it was developing these strange crinkled spots and they were spreading. This made the visor worthless.
I sent an email inquiry to Bell, and got a reply saying they hadn't heard of that problem before but they would send me a replacement. One week later (yesterday) the new visor arrived.