Bug with Landorus-Therian

I changed Landorus to Therian Forme, but before that I gave it its hidden ability, Sheer Force. Now I have a Landorus-Therian with Sheer Force and I wanted to change it to its regular ability, Intimidate. I was unable to do that by using the Dream Guru or the Wake Guru, it uses my Dream Mist but does nothing. I have reported this bug to the bug tracker. In the meantime what can I try?

hidden ability cant be changed after using dream mist.

It can, with the Wake Guru found in Nightmare Badlands outside the house you caught Darkrai.

I didn’t know😜

The only thing you can do in the meantime is wait.

According to the wiki,wake guru is bugged!