Automatic Litterbox Central

I just purchased a new PS and set it up, plugged it in. It's not as quiet as I thought. It's making a wobbling kind of sound...wubba, wubba, wubba..as the conveyer motor rotates. My cats are of course intrigued by the noise so they are constantly trying to get at it. This is not the grinding sound that others have mentioned when litter gets below the pan. This sound is coming from the side motor that operates the conveyer belt. Any ideas?

Also, the sides seem a little low. One cat got in and proceeded to fling out a couple of scoops of litter right over the side.

My cat is a happy user of a Scoop Free, but I just got a 2nd cat so I figured I'd add a different additional box that doesn't use such expensive litter.

Update: there was definitely something not right with this box. It made so much noise, like a small electric train, that my cats wouldn't use it. I called the company and they sent out another box which I just received. I'm hoping to have better luck with this one.