In Illustrator this glyph appears with a slight underline when viewed small. When it is zoomed in the underline disappears.
I can’t find any stray points or odd paths in Glyphs (Glyphs 2.2.2 (823)) that would cause this behaviour. Is there something wrong with the paths, or is it an Illustrator issue?
(Same letters but zoomed in further).
The underline/path prints at small sizes but not large.
Adobe apps apply different rendering modes at different sizes.
I suggest you simplify your path structure in the lower part of your R. There is likely an overlapping path or very small curve that could better be replaced by a straight line.
Also, consider using the Disable Subroutines parameter in the instance.
