I have read many threads discussing the need to reface a joint when both the shaft and butt are straight but the cue doesn't roll flat when screwed together. I'm curious, what happens to a cue to cause the joint to need refacing? I have a five year old cue that used to roll flat. The butt and the shafts are still straight. However, the cue does not roll flat when screwed together. My thanks in advance to all the excellent cue makers from whom I've learned so much. Chuck