Delta export trouble

Hello!
i’m new on the glyphs app and i’m having some trouble when exporting my fonts.
The Delta won’t export, all the remaining characters export with no problem.
Can someone help me with that?

Thanks.

This may be a font cache problem. Read this please:
http://www.glyphsapp.com/tutorials/eliminating-font-cache-problems

Consider using the Adobe Fonts folder:
http://www.glyphsapp.com/tutorials/testing-your-fonts-in-adobe-apps