Update: we fixed what's causing this, so any new video uploads won't experience the same frozen, out-of-sync audio issue. If you've been waiting to post–go for it! We're now in the process of fixing all impacted videos, which will take a bit more time. Appreciate your patience!https://twitter.com/TeamYouTube/status/969298199658733568 …
Hmm, check to see if you have an OS update available for your device? If not, try and file a feedback report from within the app: https://goo.gl/WdI0BK . We'll look into it.