Niantic has now resolved the Pokémon GO issue where you were able to collect the first regional sub-medal in the Butterfly Collector medal collection but the game became unresponsive with the second and subsequent medals of the day

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