Problem with Magimix 5200XL extension shaft and disc?

Hello,

I just purchased the Magimix 5200 XL and am trying to assemble it so that I can use it for the first time. The instructions say to put the midi bowl inside the main bowl and then add the extension shaft and then the appropriate disc. I have done all of that but no matter what I do I can't get the lid to close. Its like the extension shaft makes the disc too high up and there's no way I can get the lid to lock into place like its supposed to. I called the retailer who sold it to me and they don't know what's wrong and asked me to bring it back, but the thing weighs a ton and I'm hoping you can help me so I don't have to disassemble it, re-pack it and bring it back into town. Please help!