I have had an issue with my high hamstring for over a year on and off. I feel it mainly when I do heavy dead lifts anything over 100kg I will feel a stabbing pain on my sit bone. I do also feel it during squats and other motion at different times. generally there is no pain or very little pain in my sitbone or hamstring during the day. Lately I am getting constant tightness through my left lower back and erectors and I often feel a little tweak in my left lower back during extension.