[Cataclysm Classic] Rogue immune to Faerie Fire? Bug or Hack?

Was in a BG today in EOTS. Couldn’t use “Faerie fire” on a particular rogue only, other spells would work clear as day. Doesn’t seem like lag, no cloak. Anyone else able to explain this or should I submit a report?

I have video evidence:
h.ttps://streamable.com/6wn9e6