I'm aware of the display switch. I've tried playing the files on the native display as well as external. Same result.
Perhaps you had better describe your setup and PC more.
We know from earlier that you can stream to your smart tv, which sounds like you are using DLNA for that, rather than an HDMI connection.
You mention a native and external display above. Are you referring to the TV as the external display?
You have also said that you have an older machine. Specifications? What sort of PC is it? Desktop or laptop? What is the CPU, GPU, sound card, Windows build/version, etc.
You aren't using any Registry cleaner application, are you? Or a Driver Manager or Cleaner? One that stays resident and "fixes" things on the fly, or at regular intervals?
A back video screen with audio is often fixed with a video driver update, but caused by a Windows Update. As a DVD played fine with video, that implies the issue is video format related, which implies video driver. Try playing using Red October Standard rather than RO HQ. If that works but you want to use RO HQ, try the "Best Performace" Quality setting under "Options > Video > General Video Settings. If that works, try the "Balanced" Quality setting.
Search the forum for "black screen" and you will find more things to try, including backing out some Windows Update packages.
But as MC25 still works, it could still be a security software problem.