In my font the preview for some symbols and most diacritics is wrong. Mismatched symbols or (mostly) nulls appear instead of the letters. My font works ok on my machine (Windows 10). Is there something wrong with it so that DaFont couldn't generate the previews right? The font in question is Slowglass http://www.dafont.com/slowglass.font

http://www.dafont.com/slowglass.font?text=%E0%C0%E9%C9%C4%C7

Yeah I know the font works, I mean the generated previews below https://pasteboard.co/GzqSqxd.png