How to resolve this unmanaged memory leak?

I've written a small mpv renderer for avalonia using opengl:

So far everything seems to work except when i'm done and call dispose almost no memory involved with the renderer is released even though i destroy the native pointers in a safe way. I'm not sure what i am missing. Any help would be appreciated. For more context, the whole repo is here and readily reproducible: https:///www.github.com/saverinonrails/avaloniampv