I'm on Arena for PC.

The bug is this: I built a 100-card colorless Brawl deck, with the intention of having Kozilek, the Great Distortion as commander. But no matter what I do, the deck won't allow me to make this the commander. When I open the deck, the "Commander" tab at the top of the deck is empty, and I try to drag Kozilek there but nothing happens. It won't accept it, whether the "Commander" tab is glowing after clicking on it or not. It DOES accept legendary ARTIFACT commanders, like Karn, Legacy Reforged and Hope of Ghirapur so the tab is responsive to accepting commanders and the deck is full of legal cards. But I don't want those as my commanders. I want Kozilek. Additionally, NO legendary colorless eldrazi is accepted in the deck's commander slot. I tried all of them. I also checked that I'm building a regular Brawl deck, and not Standard Brawl. It isn't an issue of format legality.

Finally, I read that having a copy of Wastes in the deck can cause issues, so I removed them. It didn't help at all. Please advise.

Thank you.