Feeble Mindedness Resistant to Healing?

[Thufir]

Is it possible that not all afflictions are created equal when it comes to being healed?

Recently in SP play, I had a pretender get feeble minded. For 10+ turns I had my hero w/ heal troops ability healing, and while all kinds of troops/commanders were getting healed of their afflictions, it never worked for my pretenders FM. For maybe as much as 5 turns I was running GoH, still no luck. Then I forged the Chalice, ran the game two different times, once the pretender was cured in one turn, and the other (iirc), he was cured in two.

Does anyone know if FM is more resistant to healing than other afflictions? I suppose its possible this was just a run of bad luck, but I tested this enough to seriously doubt that, at this point. Or, is it the case that the "heal troops" command (said in the description to be identical to Arco's priests), won't ever heal FM? And/or might GoH have the same limitation?