Ranked interface bug

Strange bug.

Upon clicking accept when matchmade, the chat window shows I've entered the lobby but the round interface asking to accept and decline still remains. The champion select and everything can't be seen. I can't get out of it unless I force quit the game, and it counts as dodging.

Happens quite often. Once every dozen games.

What is this and how do I fix it?

Both the old version of the client and the most recent update had the same issue.