After doing more testing today, I've discovered something. The encoder seems to be working in one direction, but not the other. If I try to turn the shaft by hand counterclockwise, I can't turn it more then one pulse without the drive counteracting that. But when I try turning it clockwise, it seems like the encoder is not picking up any signals at all.
Do I need to bite the bullet and buy US digital encoders, instead of Renco?