I sent a support ticket and also sent a link to this thread. Will have to wait for a answer
I have deleted Uninstalled ,reinstalled and tried several different settings with mp4 files
Also tried you tube widget and anything else to do with media files resulting in the same issue

Even tried compatibility mode resulting in same issue
My specs are

Windows 10 64 bit(with latest updates)
Web designer 11 premium with all the most recent updates

Looks like it will have to be an update fix to resolve