HEVC .mp4 files Work on Mac but not Windows

UE4.27 will play H.265/HEVC .mp4 files just fine when I load them into the media player when I try on my Mac - but when I try the exact same files using the Windows version of UE4, the media player crashes!

Does anyone know why this is? Is there a plug-in I can add so Windows UE4 can support HEVC files?

Potentially it’s because I’m using Bootcamp now that I think about it. Do HEVC videos normally work for you on native Windows?

Backstory:

I’m creating a VR artwork and using large 360 4k videos as a sky sphere/cube map.

I’ve been building it on my Mac, but have now switched to Windows because I can’t seem to deploy or package the game for Quest with UE4.27 (I’ve had better luck with older versions of UE4 though hilariously).

I’m going to have 40 of these video files and I want them to be as high a bitrate as possible before its too costly for the HMD - so using HEVC files are way better for me because they’re so much more bang for your buck. Unfortunately though - I don’t know how to proceed here. Many thanks!