A broken button (and how to prevent it)
The button is very vulnerable to damage and the most usual cause of breakage is a poorly fitted neck joint. The joint may appear good from the outside but often the hidden surfaces of the joint were cut quickly and dont contact each other properly. Many times the only real contact is between the button and the neck, then, given a sharp shock such as a case falling over, the neck shakes loose taking the button with it. When I find a lose neck on a professional’s instrument I always recommend taking the neck out and resetting it properly, it’s an expensive repair but it can prevent a more expensive broken button, not to mention the sudden decommissioning of your instrument when you are on tour.