I found a problem with S3 video player in unit. When user doesn't finished the video until the end and go to next unit, the previous video still playing the sound. Or, even it runs normal with no sound from previous video (that not finished until end), the next unit become lagging. Looks like the app is still receiving data from previous video.
But this issue does not happen if a user finished a video in a unit until end, or if video is using iframe.
I suspect this issue raises because the previous unit page is not 'destroyed' when a user go to next unit.
You may replicate it on my app. Credential is below.