Gym error

Yesterday I tried to put down a gym, but when I defeated the first Pokémon this Pokémon still on the screen until the time is over... Then in each new attempt the battle started at the same time that I defeated the Pokémon before, and when I put different Pokémon to battle, the game changed to my Tyranitar which has battled at the first time.
Well, I went home after a lot of attempts, and decided to try again today... But today the same error keep occurring...
Did you have the same problem sometime?