If the animal companion dies away from the ranger, the Bonded Grief debuff appears and immediatly disappears, even though the companion is still down.
Steps to reproduce:
send the animal companion alone to fight an enemy
have the animal companion die
This only happens when the animal companion dies away from the ranger (which, I believe, triggers the end of combat, but doesn't resurrect the animal companion because he's still surrounded by enemies). The debuff works fine if the ranger is active in combat together with his animal companion.