I agree.....the sensitivity on the eyes may be set too low. When they DO sense something it means the receiving eye is NOT getting a signal(ball blocking the IR). When it does get a signal, it means nothing is blocking the ir signal. So if they always see something then it means no IR signal is getting through. That means the signal is too low......or you may have a bad set of eyes, or even a bad/loose eye wire.
It's all about the angles.