Since the last patch there seem to be a lot of new bugs with debuff Skills.

So far I've seen bugs with skills from these champs:

Alure (arena) - Floating Zzz's from [Sleep] debuff persist after debuff ends.

Astralith (arena) - Upon explosion of [Bomb] debuff the word "Unkillable" appears on the target just before it dies (target has no such trait).

Astralith (arena) - Upon explosion of [Bomb] debuff the target takes no damage. Happens seperately from Unkillable bug above.

Ignatius (arena) - Battle Shout skill applies [HP Burn] FX which persists for the match.

Magmablood (faction wars) - Green ribbon from [Bomb] debuff persists if debuff is removed

Pounder (faction wars) - Frost particles from [Freeze] debuff persist after debuff ends.