I've strung for a friend 3 times now, and each time, within about 1-3 hours, he's broken the strings in the same place (left of center mains at the top, roughly equal distance). Based on Yulitle's video, this would indicate wear on the outside, like having scraped the frame and scuffed the string or something. But I don't think that is the case 3 times in a row. This guy is not a string breaker either. The racquet is a Prince Ozone Seven. I'm wondering if there is a rough edge somewhere around one of the speedport holes? I looked, but I didn't really notice anything that would appear problematic. At first, I thought, "okay, maybe it's just me. maybe I notched the string, or make a mistake stringing -- was careless or something, whatever." But 3 times in a row now... something is not right. Ideas?