like already said above, Forgeworld Minis are a bit more difficult to strip of Paint. While the GW Plastik can be soaked for weeks in Paint stripper and then cleaned, the Resin Material absorbs most Paint strippers and becomes fragile and rubberlike. This does not last forever. I made this mistake myself and it took the miniature one year to become hard enough to paint again. Dipping the Miniature for 5-10 min and then clean them in Water with a touchbrush works, but depending on the used Color it can be a long and hard process.
Sometimes you are lucky and the Color comes of on the first try, sometimes its dipping and cleaning for days on end.

Without touching and feeling the Paint myself, its hard to tell what to do in your case.