We built our icon system using 2 sets of component groups. One group that we use for the source artwork, which includes 2 sizes and filled/unfilled variants. The second group is used to resize the icon. 

The source icons have their color set to our default color style for icons which is called ‘icon-primary.’ Most of the icons can have their color overridden by designers (often to icon-secondary) but recently, some of the icons just can’t have their color changed. It seems totally random. Most are fine. We’ve dug into this and there is no difference between layer naming, flattening, constraints, autolayout, etc. between icons that work and icons that don’t. When an icon is detached, it can be recolored. Help!