I tried this in Portal 1 and with both v 0.7.0 and 0.6.0 the game will occasionally not catch me releasing A and get me stuck walking towards the left.

A theory on why this happens:

• Some Keyboard input is inadvertently captured besides the simulated gamepad input, but the release isn't.

I think this might be the case, because on my other monitor the tester shows the gamepad stick movement just fine.