Unable to Update Branch Permission

I'm unable to update my project branch permission. I was trying to add more names to the Merge Pull Request permission. When I click 'Save' I'm getting error in the dev console. Refer to the attached screenshot (Screen Shot 2018-03-21 at 1.14.26 PM.png) with the errors on the dev console.

I'm also noticed when I opened the edit form for the branch permission, it does not load the existing names for the Merge Pull Request field. Notice on the list screenshot, it has few names under Merge Pull Request. But when I opened the edit form, the field is empty. Refer to form.png and list.png.