Amiga Power Stick controllers

[Zenimus]

I picked up two of these hoping to get a nice functioning Colecovision controller, but even these have functionality issues. One seems to work fine except that the left direction doesn't work. The other controller is even more bizarre: every direction and fire button registers as UP. The keypad seems okay, but press anything else and your character only goes up.

 

Does anyone have any advice for fixing these? There's 2 screws in the back, but something still holds it together after those are removed and I can't seem to open them up.

 

I have a Power Stick for Atari 2600 and it's a nice controller. How could these Colecovision versions be so wacky?