I have created a library of icons, some harvested from an icon library, some created in Illustrator etc. The icons are all vectors set up as shown:

I have used these icons in buttons with 2 states default and pressed, the pressed state is the inverse of the default - simple monochrome. The colours are selected from a colour style:

the buttons incorporate an instance swap for the icon. The issue I am having is that when I insert an instance of a button in the pressed state the icon in the pressed state behaves randomly, sometimes remaining black when it should be white. Default state is always OK, random behavior always occurs in the icons that have been recoloured in the pressed state. I am sure there are some best practices for creating icons and I am doing something fundamentally wrong. If anyone has a foolproof method for ensuring icons respect the colour state set in the button variant I am all ears!!

full disclosure: not all the icons are noe set up the same as I have been experimenting with adding unions and flattening after reading some threads but havent been able to reliably solve this predicament:

Any help appreciated!!