Well, for some reason the ports on my phones would always kind of stop working at some point unless I held the headphone jack in at just the right angle. It wasn't the headphones because they would work fine on other devices.
> Well, for some reason the ports on my phones would always kind of stop working at some point
Lint. Headphone jacks and lightning ports on every iPhone I've ever owned would always stop working properly after 6 months to a year of being carried around in my pocket. (Sort of) easily fixed with a paperclip to pick the lint out of the port, of course, but annoying and the headphone jack was harder to clean than the lighting/dock connecter port.