Unless it's a new update, this behavior of Morty's Gengar wasn't happening, because being a ghost type, he was using shadow tag and he never changed it.
I was playing the boss Morty and using wynaut with shadow tag as the first pokemon to kill the mega gengar, however the gengar in form managed to be changed and when I was in froslash my game froze and crashed giving me defeat against the boss. How to proceed with this problem?