Code in mark & mkmk feature

For an algorithm that creates horizontal fractions, I need to use the mark and mkmk features. If I write my own code, the compiler complains that my lookups are duplicated,
while, in fact, they are not. If I select auto-generated code, the compiler complains of duplicate definitions for “mark_DFLT” and “mkmk_DFLT_bottom”. Any idea how to get out of this maze? Using Glyphs 3.1 under macOS 12.5.1. I don’t remember having such problems with similar code under Glyphs 2.

What lookup names did you used in your own code?

NumBar and DenomBar
However, I’ve tried other names such as pos_2, result in the same complaint by the compiler.
This seems to be a very basic error in the compiler.

Can you send me the .glyphs file?