HTML5 Playback Synchronization
I've written on this problem before. It's getting hotter now. Timing of audio and imagery is screwed up in Chrome. Now I'm getting feedback from major accounts that includes iPad/Safari is also blowing the timing.
Here is a direct quote from a major client: "iPad on Safari browser: video lagged pretty far behind the audio and the course kept crashing. She took this course from the head office" (meaning bandwidth is plentiful in the head office).
Articulate Storyline has had problems like this (and the ligatures problem of "t" and "f" not displaying) for more than a year now. I don't see other authoring systems reporting these issues in their forums.