Turbo Mode (shift+click) the green flag. Without it it'll become desynced. I made a lip-sync engine! See the forum for how to use it: https://scratch.mit.edu/discuss/topic/178567/ It's really easy!
To test, I lipsynced the chorus to TiK ToK by Kesha. Let me know if you'd like to see it become a full lip-sync song! I'm using my new style, which has me wearing clothes. I did this to make me stand out a little more from the other stickfigure styles. I move around and change size to show you that the lip-sync engine will sync up with the character! See the forum for the changelog: https://scratch.mit.edu/discuss/topic/178567/