Thank you! Yes, I am using an old version of Game Maker, specifically v2.3.6.595. Unfortunately, updating Game Maker actually breaks the engine I use to make the game. This scenario about porting it is the first time that's ever been a problem, so perhaps I could try manually adjusting the engine at some point but I'd have to keep it low priority.
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I don't know if 2.3.6 actually has any of those modern video functions--maybe it's pretty close to the cusp? An alternative could be converting the videos to sprites and playing them that way since the audio and subtitles are separate already. I'll stress there is absolutely zero pressure to follow through with any of this--my note was only meant to be informative.