Use of undefined glyph class, @_A, on line 705 of

[alexmyczko]

What's wrong when I get above message?

I get it with the B612-Italic.ufo
http://sid.ethz.ch/debian/fonts-b612/fonts-b612-1.003%2Bgit20180121/sources/

$ ufo2otf B612Mono-Bold.ufo
double free or corruption (fasttop)
zsh: abort      ufo2otf B612Mono-Bold.ufo

$ ufo2otf B612-Regular.ufo
Use of undefined glyph class, @_u_accents, on line 150 of 
...
Expected ';' at statement end on line 252 of /var/www/debian/fonts-b612/fonts-b612-1.003+git20180121/sources/B612-Regular.ufo/features.fea
There were errors when parsing the feature file and the features have not been applied
zsh: segmentation fault  ufo2otf B612-Regular.ufo