Differing kerning for numr and dnom

[SCarewe]

Hello, I am running into an odd issue. I have my numr glyphs set up as components (align=3), so exact same sidebearings as my dnom glyphs. Kern On wants to kern my numr differently (slightly tighter) than my dnom. Why? I have them both in the same special spacing group. Saving and re-opening the file didn't change anything, just like trying a different special spacing group. Do I need to re-define models for every set of glyphs (dnom, numr, superior, inferior)? I thought this was intended to be taken care of. Thanks for any pointers!