That happend to my SP 900 SA - The at least 4-5 grommets on the top of the head were shot (over time), which caused my Gosen Pro 66 (at 23.75 lbs) to break very fast. The first time I had the string with the racket, it lasted long. After the next series of string changes over time, the was lasting shorter and shorter until I had a close look at the grommets and noticed the top center had splits with sharp ends on it.

The problem has been rectified since the grommets have been changed out with new original Yonex grommets.