Aftermarket buds lose sound in one side; iPhone 6

Since I upgraded from 5 to 6 iphone, four sets of aftermarket buds lose sound in one side, the left. All good quality buds. I get a couple of weeks out of some, days out of others. I can't find a solution and need my music from both ears so I keep buying more! Tired of it. Once was strange, twice was a coincidence, four times is an issue!!

Help appreciated; and no, it is not earwax. Just goes from perfect sound to no sound, only one side.

Thanks!