Square flashes after the game ends

I’ve had the following case a few times already:

  • start an OTB game
  • play until conclusion
  • one of the squares starts flashing after the game ends

In particular, for a game played yesterday i can provide more details:

  • the game was initiated from the app
  • played until white resigned through the app interface
  • the whole board flashed for a few seconds (this is expected)
  • after that, a random square started flashing with purple