I have been experiencing some issues with the Search Results web part. (everything worked just fine until the first upload of a .mp4 video)
The query works fine as the file is being shown in the results. However, it's being pulled with the wrong link. Not directly to the file to be opened / downloaded but to the /Form/Display Form item id -> which means that when accessed the search result sends the user to the document properties.
I need to mention that if i access the file directly from the list it works just fine but the users are not supposed to access that part of the page due to confidential info.
@adrianion It's almost 4 years after your post and we have this same issue in our SharePoint document library (classic site). Did you ever get a resolution?
Our workaround is to post files in a different SharePoint site librray, generate shared links, and post those to the main document library, which then show in Content Search and play as expected. It's tedious and I'm hoping you found a solution.