The skill Morph states that it will change your summon into your secondary one “while maintaining its previous stats.” This is, however, not the case. Take a 10* Temple Shooter, Morph it into a 1* Temple Shooter, and its damage will sharply decline. I went from 2700 to 2100 damage myself. The point of Morph is that you can use a second card without having to rank it up. This bug hurts this skill extremely, please fix it, danke.
My speculation suggests that the issue is the Summoning additional damage is not being applied. This might have something to do with when they readjusted the Summoning damage formula to be less initially but greater with levels. I’d start looking there.