I got Sonic Lost World for Christmas, mostly been lovin' it. I was at my grandmother's the first few days after I got it and it played very smoothly, even two rooms away from the console (slight lag occasionally simply from being away from the system, but nothing else)! However, since I got home, I have had multiple issues with stuttering sound (sometimes in speech, like the Deadly Six's mid-level taunts, and other times in music), and worst of all, a complete freeze during a cutscene! This freeze was especially annoying because it was post-stage and I had lost my progress on that level, and now every time I finish a stage I'm scared to death it'll happen again to the point I can't even enjoy the cutscene. 
Other than Lost World, I did have ONE instance of music stuttering in Dr. Luigi, while Super Mario 3D World and other games have worked flawlessly. After the Dr. Luigi instance, I moved the system so it would be closer and less obstructed between it and the gamepad, and now I only continue to experience issues in Lost World (so far only in stuttering, but I've only completed two levels since because I'm deathly afraid of another freeze).
I think I may know the issue. I was able to obtain a Wind Waker HD edition gamepad recently from a private seller. However, when I went up to my grandmother's, I brought my original gamepad instead so as to not damage the new one in any way. Since I started using the Wind Waker one after coming back home, I'm thinking maybe because it wasn't the one packaged with my system, the connection between the two may be faulty. Anyone know if there's any credibility to this theory, or what the issue may be? I'm playing a downloaded copy of the game through the system memory, if that makes a difference.
Thanks!