Audio cuts out on left side while using headphones

I have a Macbook Pro Late 2011 with a 2.4ghz processor speed, 8gb memory, and 500 GB hard drive. My operating system is OS X 10.11.1. I had it repaired (trackpad replaced and keyboard replaced) a few months ago. Since I've gotten it back I noticed that the audio seems to slowly cut out on the left side when I use headphones. I have to hold the headphone jack in a certain position, put the volume on high, and use the test audio connection button to get it to work but only temporarily. It then eventually cuts out again, especially when I play anything at peak volume level. I've tried everything including different headphones but it's always the same problem. What does anyone recommend I do about this?