OTF not exporting in 3176/77

I get this mark feature error in 3176/77 whereas I didn’t in 3151 and below. I’ve been looking at the feature file but cannot figure out what’s wrong with the code (i.e. not seeing any obvious typo in the code). Any suggestions or insights on this?

On a totally unrelated note, Generate Glyphs dialog now interprets = as the actual ‘equal’ glyph.

Can you send me that file?