Is the button just a click button or a scrolling/twisting knob? If it's a potentiometer style knob, it could be that..
But anyways.. sounds like the end in that goes into a phone is good, and the part that goes into my headphones looks like the one above I posted.
If the end that plugs into the headphones hangs, it could be a loose plug, and the connection is getting to be pretty poor. If so, I'd find tape or wrap it around somehow to keep it from drooping. Something else too, is the volume at which they've been played at. If they've been relatively used at medium to high levels (like someone standing ten feet away from you can remotely hear it) then the gasket, housing, voice coil, or suspension could be damaged, meaning it could very well be trash.
I'm not sure how you'll be able to change the levels quickly... I need more info as far as if the drop occurs momentarily (less than 10 seconds), or is prolonged until you fix it.