Did you report it? I always be sure to let the FA know of broken seats or audio, and they're usually grateful that I told them so they cna get them fixed.

I've found that UA's style of headphone ports are prone to breaking. The single jack (as opposed to the double that you see on some other carriers) is more prone to becoming loose. I suspect the double jack lasts longer because it's easier to dislodge the single type jack as one sits down or leans in that direction.