I have a Galaxy s6 Edge and my problem was stricting my snapchat videos being out of sync when recording with the front-facing camera. I could play other's stories fine with no lag. And the recorded videos through my phone's default video app were also in sync.
I tried to disable Nu-player but that wasn't an option when I went into the developer options. Other things I tried, all of which didn't work, were turning off Ok Google, turning on Power Saving, and clearing Snapchat cache. I also tried the last suggestion of using the speedy filter first and that didn't work for me either.
Then, finally, I read somewhere to turn off S Voice. And that did it! Hopefully this helps someone else 
