You wanted a cuemakers opinion, well you've got one. I have been making cues since 1986 & in that time have seen this often. This break is caused by breaking the balls with the cue & at the end of the stroke, LEANING on the cue, so that the shaft goes onto the table & bends. Even at 160 pounds a 19 once thin piece of wood doesn't have a chance. This type of breaking causes the flexable shaft to bend, until it gets to the joint, where it is stiffer. The joint area is the strongest, because of the 3 inch bolt in that area. Cues break in the area, just behind the end of the screw (just as this on did). It may take some time, but eventually small cracks are formed in the wood. Then one day you drop it or hit a ball off center & the wood can no longer flex, so it breaks. Your friends cue was not intended to be used in this way. IT WAS ABUSED. I have a box, with a dozen broken, just like yours...JER