Hey!
I think I know what was happening with the "bug" I was experiencing. When I was using WASD, I could use B for selecting. But, when I was trying to play after that session, I used the arrow keys, where B isn't the button to select the character.
It does make sense when you are playing with another person locally, and it is mentioned in the controls, but when playing alone, maybe the B, G, Y, and H keys should be compatible with the arrow keys too.