I have a short .mp4 video in a folder, selected it as my custome splashscreen. Restarted system and it worked beautifully. The issue is that it only works that very first time, when I restart the system the splashscreen video doesn’t work anymore.
So I select the default splashscreen, restart the system, reselect my custom splashscreen video, restart system and it works again. But again only for that one time right after I select it. On subsequent restarts, the video doesn’t show anymore.