Encoder Difficulties

We are currently working on the BaneBots 220 Encoder Block with Encoder (am-2885) found here: http://www.andymark.com/product-p/am-2885.htm. We are unable to find a manual on putting it together. We have run into a complication; the 3-D model that we are using has shown the encoder to require more parts than provided in the kit. We ultimately are unable to lock in the encoder disk to the shaft. Has anyone else run into the same problem and found a work-around?

Team 2225