I was on a United flight a couple weeks ago when the passenger next to me told the flight attendant that his headphone jack for his seatback IFE was not working. The flight attendant offered to reset the IFE. The passenger declined the offer. I'm still wondering whether the flight attendant was going to reset the IFE for everyone or somehow for just that passenger.

Whenever I've had it reset, it was just one chair that had to be restarted.