I looked at your font and confirm your problem. In fact I do have the same here. I decided to generate my fonts as TrueType, which works, but it's just a workaround. I think, this is a general problem with FG 5. There is another font designer, "Glyphs". This has a lot of other problems, but I re-generated some of my fonts with its trial and they are working now.
HTH, let me know.