Thank you. This at least gives me some insight into what the problem may be along with some potential solutions. If I happen upon a fix, I'll let you know.
Sadly, it looks like I won't get to play Ossuary. I tried changing the compatibility to Windows 8, reduce the resolution of the application, and disable high-DPI scaling effects (among other things), but nothing worked. It's unfortunate because it's clearly a clever game: I like the writing, the world-building, the weirdness, the mystery. And I got interested in the first place because Extra Credits introduced me to The Majesty of Colors.
On the off-chance you ever remaster the game, I'd love to play it.
Thanks for the update and all your patience! We're sad about the issue and we'll keep an eye out to see if we hear about any more clues for what might be causing it. If you got the game on its own (i.e. not in one of the huge charity bundles), feel free to request a refund by contacting Itch support and letting them know we couldn't solve your issue: https://itch.io/docs/legal/terms#refunds