Google play movies download mp4

I have a similar issuebut I'm going to add a little twist here.

So I purchased the Wolverine DVD from Walmart, it came with a digital copy and a code to be able to download a copy from the Google Play Store. I did this, and then decided to move the movie to my external SD card. When I try to play the movie, it hangs during the "Universal Studios" opening at about 12 seconds in and then displays "Video cannot be played". I've downloaded countless different video players, but all have the same result.

Now here's the twist I used a file explorer app to locate the video folder and selected the movie file, it gave me the options to select which of the many video players installed I wanted to use to play the movie, I selected the stock player, and played the video through there instead of opening it from a video app directly, this time it worked! The movie opened, and played fine, but when I stoped the movie and tried to use the same procedure again, it failed and now displays "Video cannot be played" yet again.

Now no matter what I try, I can't get the video to play. This is very confusing, how can it work once, and then not work again, almost as if it got corrupted? Any input would be greatly appreciated.