I think there is a falcon bug, where the damage resistance does not go back up even after the "Fangs Out" ability ends. I have noticed this under the following conditions -

1. Falcon is attacked by a robot when "Fangs Out" ability is active.
2. The duration of "Fangs Out" ability is over.
3. The same robot attacks again after "Fangs Out", still the 66% resistance does not go up.
4. I have noticed this only in case where the Falcon is attacked by Embers but it may be true for other weapons as well.