When i used Ability Capsule on Delta Muk to change its Ability to Regurgitation , the Game Crashed 
Not sure you can change non HA to HA without dream mist. It’s usually used for mons with more than one basic ability.
Regurgitation isn’t an HA iirc and the one you find doesn’t come with HA.
A lot of people have recorded crashes when changing Delta Muk’s ability. I think it has to do with sprite changes.