The app is exhibiting behavior reminiscent of a memory leak. If you stay on the chat section (group private chat) for too long the app dies. It will die faster if you are interacting in a chat. Also, the creator of private group chat (called club) is the “owner” so if the coach didn’t create that group, then they cannot add members. There should be a way to assign admin privileges to private group chats so that one person is not solely responsible for the administration.