adjusting caption timing issue

Hi Craig,
we are experiencing problems with the caption timing when we are editing the captions. We are finding blocks where the timing  “jumps” and so when the video plays the captions don’t come out at the timing of the video. it happens only in sections – mostly in the middle of the video. This only started happening two days ago. can you please investigate the error? it’s been time consuming and frustrating for us trying to correct it, and even if we reload the page, and even if we delete and reload the video the same error happens at the same point of the video. Thank you