Lobby Player name Touch Keyboard issue

Hi to All,
i am developing a multiplayer game. the dedicated server runs on Windows and the client on Android.
When i start the game everything in the lobby (i use the unity lobby prefab) works perfectly and i am able to join the match and input the player's name.
after the first match when everyone is sent back to lobby if i try to edit the player's name the input keyobard remain open only if i keep pressing the input field.
does anyone know how to fix this bug?
thank you all