I think I have this fixed now. Thanks for pointing out the issue.
The code was checking for the existence of the file (and the code was limited by that MAX_PATH limit), even if only to update the DB. In addition to that fix, I'm also adding support for longer than MAX_PATH to related routines. I was aware of this problem but I never got a complain about it, so the fix got postponed.
And it's nice to know that Windows 10 version 1607 has a nice opt-in workaround for apps that already use the Unicode versions of some of these WinAPI file management functions. Thanks for linking that article.