I thought this was me, as well, that the devs had fixed the Tuesday reset bug. I set my teams, go clear the dungeons or PvP, and sometimes they are reset when I check them so I set them again. Then, before leaving the game I swing by one last time and verify that they are correct before I log out. Unfortunately, this week they reset on me. I can't explain it, why they are not "sticky". I set them, go do a PvP match or the dungeon, they may or may not have reset, but I was thinking that as long as they didn't change before my last check of them that I was good to go. But, not this week.
Edit: FWIW, this is on iOS, perhaps it's not an issue/bug on other platforms/OS?