So I'm working on finishing up 9.2 before tackling the crucible, and I think I've hit a bug, but Happy to have it explained to me like I'm 5.
9.2.5 has a path where they need to be armour broken to deal damage, but they're immune until they're knocked down. Ok. But what's happening is I knock them down, remove the immunity, then when they're knocked down again the immunity comes back as well as the removal cool down! I have to wait out the 25 second cool down before knocking them down again removes the immunity!