We are aware of the following issue in the game.
For moves that attack multiple times in succession, under certain conditions, the animation displaying damage dealt will not play, and it will appear as if the enemy was only attacked once.
Note: This issue only affects the animation. The damage dealt is being properly reflected.
From 8/28/2019 at 10:00 p.m.
This issue will be addressed in a future update.
We sincerely regret any inconvenience and hope you continue to enjoy Pokémon Masters.