Error “Is this lightning adapter connecting a pair of headphones?” when plugged in

The first thing I would do is clean out the charging port. Under a bright light, with a magnifier, if you have one, use a non-conductive tool like a toothpick and carefully remove any pocket lint or other debris that may have gotten jammed into the port.

krisztian256 wrote:

Yes, cleaning was the first thing, did not help (in both cases, months apart). Else, the problem came up when it was connected, probably no extra debris could have gone inside.

Debris could have already been inside, but if you've cleaned it carefully (I'd give it one more go. It's astonishing how stuff can get pushed all the way to the back of the port and get smashed so flat you can hardly tell it's there), then I'd guess that there's something wrong with the port. I'd arrange to have Apple evaluate it.

Genius Bar Reservation and Apple Support Options - Apple

Meanwhile, you might consider BT headphones.