I was surprised to see that I had only 66/67 glyphs of the Cyrillic > Bulgarian set. It turned out the missing glyph was «yu-cy.loclBGR». This is a misspelling of «iu-cy.loclBGR», which I did have in my typeface… it should be corrected in that list.
We renamed the iu-cy to yu-cy to mach the unicode name and the general romanisation rules. It seems that the renaming wasn’t done properly as there are still several places that referred to iu-cy.