one of my lessons hits the PK Ki15 and I noticed it was making a wierd sound at times. I asked him about it and he said sometimes it feels like it is broken..i hit a few with it. I found that it was solid as can be within the sweetspot, but when hit high in the stringbed it made that wierd sound and there was some shock and lots of vibration (almost like a rattling) and it just felt weak in the upper hoop. The frame is pretty new and was not abused and I could find no visible sign of cracks. I dont find that acceptable, but an wondering if the PK people think this is normal for PK frames? I advisd him to see if he could return it. guy already has tennis elbow.