Same issue here with the last insider build (if I put the mods directly in skyrim folder they work fine, but they don't work from MO anymore, so there's an issue with the VFS / hook). I've read the release notes to see if something in particular could have caused this but nothing stands out. Still trying to find if some new security features prevent the hook from working, I've been at it for hours. We have to find a solution, otherwise people who use MO will have a bad surprise when the fall update for Windows 10 comes out.