I just had a game where i could not FR a LE Dark Knight. Once he died and came back I was able to. No sure if this affects other LE's or not. Just remembered separate issue. Someone vortexed my Ireguard on elemental plateau, animation happened and he lost his spell but my guy stayed where he was. probably because of no available space behind shrine(current map set up, no champs/relics back there)
The dark knight likely had "warding" upgraded and could thus not be the target of fading recollection. I have had the same bug with vortex, though. Someone tried to vortex my cyclopse hurler on elemental plateau and it stayed exactly where it was.
Lich Born. "This unit cannot be the target of spells. When this unit is destroyed, it reanimates as a Lich Knight champion, loses Lich-born, gains +1 DEF, +4 DMG, Flight, Scorn, Life Siphon, Immunity: Magical, and gains Attack: Magical as its basic attack." Does not specify whether it's friendly spells or opposing ones. So that might be it. Perhaps both.