Rough Cut Issue

After watching the rough cut that had been uploaded to youtube, I noticed that the lip syncing did not seem to look completely in time with the song, despite it looking perfectly insync on final cut. After getting my sisters opinion on the rough cut, she also said she noticed that the timing was not right. This may be due to the fact that it had been uploaded through youtube. We will need to make sure the timings are correct on final cut & when it comes to uploading our finished piece, everything is still in sync & in time.