Failing to load Precached Media Source receive the below in the log:
LogWmfMedia:Warning: Failed to finish resolve file://D:/Builds/Releases/QAGame/Content/Movies/MediaExample.mp4: The byte stream type of the given URL is unsupported.
LogMediaAssets:Verbose: Media Info:
This also happens when trying to play the source in PIE.
Result: Source fails to load
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-34285 in the post.