I also have this problem. For several expansions, at time adding Custom debuffs stops working, and then latter a fix is made and they all work. Right now I cant work out what Healbot version to revert to.
I can not get Frenetic Charge to display on Queens Court. Some custom debuffs I add work. Bioluminescence works on the boss on Blackwater Behemoth but not on the trash when you get the Puffer fish buff in the tunnel to the boss.
I wonder if it is related to numerous spells with the same name.
Another example is "Mind Tether" on Za'qul. I can not track that debuff while we try to solo tank it.