Chosen Solution
After Changing my IPhone 6s Battery My Headphones Now Play One Side Only I Tried To Test It In Another Device And It Working Fine But In My IPhone It Only Play One Side I Think The Bug Is From The Phone Not Of Headphones And I Tried To Clean The Port And Rebooting My Phone But Nothing Worked But On Other IPhones My Headphones Works Fine U Have Any Fix To Try
It;s possible that you damaged the Lightning/Headphone flex when you replace the battery. You could always double check your work by following this guide. Your problem may be coincidental but unrelated so you should also shine a bright light into the headphone port to see if it is dirty. There are a few metal contact points that spring back and forth. If they are dirty, sometimes they get stuck and don’t make contact with the headphone jack. You can try to clean it out with a bit of alcohol and a fine tip cotton swab. Worse case, you could replace the Lightning flex yourself by following this guide.
