The usual cause of a broke phenolic ferrule or tip is because it is shaped wrong. To often the tip is shaped to flatly as the player or mechanic is attempting to be more apt to hit center ball. This allows the tip to get much closer to the balls edge before the miscue occurs so that the very edge of the tip, where it is not well supported gets way to much pressure. If the tip is a little more arced, the miscues will happen a little more frequently but the more centered part of the tip, where it is much better supported will get the brunt of the force. I've repaired dozens of this type of damage over the last few years.
Dick