I’m sure I have had sliders mishave like that, too. Mostly I just don’t want a slider in the first place; I prefer feeling for the volume up/down keys and tweaking the volume bit by bit, sometimes using modifier keys for extra precision. It is incredibly easy to input “slightly louder” in the old way. It is unnecessarily hard to input “slightly louder” with a wonky touch slider. And, at times I have blown up the speaker by touching it the wrong way.

You can just flick left/right on the volume/brightness icons to adjust a single increment, without having to bring out the slider. This isn't documented anywhere, it's another one of those hidden features you just have to learn.