Defective product, unsafe - Grivel Stealth Helmet

I used this helmet just once for single pitch sport climbing. I didn't take any falls or subject it to any impact but toward the end of the day my climbing partner noticed that the helmet had developed a significant crack in the foam above the right ear. This is extremely disappointing. Another person at the climbing area said they had had the same experience with this helmet. Obviously, I will not climb in this helmet as it is unsafe.