[CLIENT] Team Builder Champion Skin selection bug
Basically, when Team Builder memorizes your champion and skin from your previous game, it creates a situation where both the default skin, and the skin from your previous game are selected. It's not only a visual bug, since that the default skin will take priority over the previous game skin when taken in-game. Reselecting the default skin and choosing your previous game skin fixes the issue.
EDIT: Just another thing to add. The bug is not visible unless you select another skin. If you select the default skin, your previous game skin and the default skin will be selected. If you choose another skin, that skin and the default skin will be selected.