The strangest thing just happened: From the SmartThings app I went into SmartApps and tapped “ActionTiles”. Then I got a network error and the entire SmartApp disappeard. I checked in the IDE and ActionTiles has actually been removed from my account.
Alex’s suggestion seemed to fix it. I logged out (“removed”) of Samsung and then logged back in and I’m no longer getting the symptom. Thank you, Alex!