Error with generated font on Quark

This might not be the right place to ask, but I figured it might be worth a shot.
I got a report that one of my fonts is generting an error when trying to create a PDF from an old version of Quark:
%%[ ProductName: Distiller ]%%
%%[ Error: invalidfont; OffendingCommand: definefont; ErrorInfo: StemSnapH --nostringval-- ]%%

What puzzles me the most is that only some family members throw this erros, and not others, when all of them are generated from the same glyphs file, with no major differences in parameters

Does anyone out there have a clue what the error really means and what can possibly cause it?

Quark XPress has had mediocre OpenType support. What are your grid settings in File > Font Info > Other Settings?

Grid spacing: 1, subdivision 1

It’s Quark 8.5, to make things worse. I can’t even install that to test :frowning2:

StemSnapH is your horizontal stem in File > Font Info > Masters, make sure the values there are compatible for interpolation (same number and order of values). Perhaps export a version without any hinting.