Niantic has updated the official Known Issues support page for Pokémon GO. Read on below to learn more:
Trainers cannot tap “ok” when claiming second Butterfly Collector medal of the day.
Trainers cannot tap “ok” when claiming second Butterfly Collector sub-medal of the day.
Issue description: Trainers are able to collect the first regional sub-medal in the Butterfly Collector medal collection but the game becomes unresponsive with the second and subsequent medals of the day.
Issue status: Resolved.
Source: Official Pokémon GO support page