What could be wrong with Feature code in imported file

Glyphs
#1

I have exported FontLab 5 fonts and successfully brought them into Glyphs, except that when I try to compile the OpenType code, I get the singularly unhelpful

The operation could not be completed.
No other information is available about the problem.

Could the fact that the font includes double-encoded glyphs be the issue? If not that, what are other likely culprits? It has pretty complicated classes and features, but I’m not spotting any obvious errors.

#2

Can you send me the file?

#3

Sent!

#4

The font is saved in an unusual format. The code path hat reads it has a bug that reads some wrong values that cause the export to fail. Save the file once and reopen it should fix it. And I fixed that issue for next time.

#5

Thanks so much for the help!