Android PlayFullScreenMovie only works on development build

In my game for Android, I sometimes play a 3 second long video using Handheld.PlayFullScreenMovie(). This has been working just as expected every time I build the game (for months now) except that when I try to build the game as a Development Build (by checking the box in the Build Settings) the movie does not play. Everything else in the game works fine, but when the movie should play, the screen instead stays as it was and freezes. No buttons work, and I have to quit the game.

Any ideas as to why building as a development build might cause my videos to stop and my game to freeze? I use the boolean Debug.isDebugMode before Debug.log but I am not using that boolean before anything other than logs. I was under the impression that building as a development build only changed that boolean, so I cannot understand why my videos are crashing.

I've tested back and forth a few times now, building as a development build and not as a development build, changing nothing except for this, and the videos work consistently when it is a development build and consistently cause the game to freeze when it is not a development build. So strange!

I'd be grateful if anyone has any ideas or clues or hints at all. Thanks so much!!

(fyi, using Unity version 5.3.2f1 Pro on a Nexus 5x)