Some YouTube users, myself included, are having issues when they upload a video to YouTube. Once the video has been processed the first few seconds are just grey/pixelated. Fortunately there is a simple solution…just add audio! I only get this problem with videos I upload to YouTube with no audio so I tried just adding a single 1 second audio sample at the start and reuploaded the file to YouTube. That resolved the issue.
Original upload without audio and hence faulty at the start: