Hello All:
Thank you for the details. There are a couple of things I would like to suggest or get additional feedback on. Before we go into that I did want to highlight something that has been mentioned in this thread. It looks like a refresh of the OS does resolve this issue for many. For anyone having this issue on an RT, please try this and verify that the issue is no longer present.
One thing those that have yet to refresh might try is to uninstall and reinstall any applications being used to view these videos. I have seen some reports of issues like this being related to applications that do not get all the proper updates.
Besides the refresh one other thing I have seen some reports of causing this issue are troubles with the audio or audio enhancements. Please go to the desktop view on your Surface and tap and hold the volume icon. Select sounds from the pop up menu > go to the playback tab > highlight the speakers option > select properties > go to the enhancements tab > check the "Disable all enhancements" box > tap OK. Once you have done this, restart the Surface and try the videos again.
Please let us know if you have any new details to share regarding this issue.
Mark W.