riding out of the city the other day with, wearing an agv xr-2 - agv's top of the time helmet. sweltering at the stoplight so i crack open the face shield one notch. just barely open. light turns, i accelerate to about 35mph and turn to check if anyone is next to me. WHAM! visor flies fully open and flies off into traffic. what is that! yes i'm 100% sure it was mounted correctly. is this a usual occurance?