Exported file does not match Animate file

I have created an animation in Animate CC for a guitar teaching app I am creating. It has the printed song scrolling from right to left while an MP3 of the song plays. It also has the chord symbols change at appropriate times in the animation so players will see when they should change chords. It works really well within Animate: everything is perfectly correlated. But when I export to movie (mp4), the scroll rate for the printed song changes so the chords are not changing at the right time. Has anyone had this problem? (It goes thru Media Encoder, so it changes the .mov to an mp4 using H.264 codec)