Locking in Champion

Hello, Sometimes I am in the in game lobby and it won't let me lock in a champion. Because of this it kicks me out of the lobby and I get a leave buster which makes me have to wait. This costed me a game in my promos to Silver 1 and I would like to know how to fix this. My brother plays on the same internet and this only started happening recently. I would like to know is something wrong with my client or how do I fix this.

Thank you for your time.