Reviving this thread...a friend has a GT3 driver and it rather consistently comes "loose" - head doesn't fly off, but it certainly isn't locked on to the shaft any longer. I have a GT3 as well and swapping the shafts out, mine never has an issue. Additionally, the questionable head has more resistance when trying to swap shafts. It had done this before so we swapped out the set screw and it is continuing to do the same.
Is there anyway in which there is something going on in the head to cause this problem? I would think it would have to be an adapter or set screw issue - but when it happens with every shaft and those same shafts work fine in my head I am at a loss.
I'll call Titleist on Monday, but wanted to see if anyone had any thoughts on it. Thanks!