That’s… not Maw-Mercy, that’s a dungeon.
(Maw Mercy Invade, Whitehelm Banner = the top of my list)
Yup, that currently happens in explore every time, actually. You can do fun stuff with it, but it’s impossible to make the banner name change without reloading the enemy team. I faced a team of Goblin King, Amira and two other females in explore yesterday, put Grapplepot in a team slot and named it “What the hell?!” and tried renaming my first team into “Crap, the wife!” in hopes of a funny screenshot. But alas, the name change of the first team only registered in the next battle and of course I had a different, random explore team to face then.
I’ve got exactly the same issue. Since this bug doesn’t affect gameplay, I imagine it will be with us awhile…