I just found a bug in the mediafoundation videoplayer. It seems that switching between two “similar” videofiles (same aspect, codec, etc.) is causing an error. The video is playing but the texture seems to be broken. Switching to another video with other format is “fixing” this error.
Couldn’t upload the GIF because of the upload-limit, but here is the link to the Element-Post:
Good news: No need to give you the files since the error occured because of an old mediafoundation-version also laying around in the gamma-preview-folder.
But: Why is a fresh-installed preview picking up an old one and not using a newer one by default.