@chainik
Yeah playing a file from both drag+drop into the MPV window, and the SVP menu works fine. MPV and SVP both work.
edit: so I installed "plex media player" to test as an alternative, exact same behaviour happens :\.
edit 2: got Plex for windows to work, some very old legacy versions of vapoursynth and other libraries that I'm pretty sure where conflicting with newer versions that had remained installed and windows did not properly remove.