This started about a week ago but I just started to notice it. The audio and video don't sync if a video is streamed in the iPhone web browser; the video seem to be running slower than the audio. If downloaded or viewed using the giant bomb video app, the video is choppy to the point where it's about a frame or two per second but the audio is fine. Other video services such as youtube are unaffected and until last week giant bomb stuff worked fine. Not sure if this is on my end but did some basic troubleshooting and couldn't find anything.
EDIT: Tested with watching Giantbomb on youtube both on local networks and using 4G and none of these issues show up; the videos play smoothly.