Whisker review: Litter Robot 4

I have had this unit for less than a year and lately it has been making loud scratching sounds. We took it apart yesterday to clean and when we went to put it back together, it won't work not. The grooved on the globe are not far down enough to the gears. I have not only spent $799 on the unit, I also purchased the hopper for another $100 and to get 7 or 8 months out of it? It was purchased at Pet Smart and I am going to try and track down when it was bought and it was a cash purchase so I need a receipt from them. My son threw the box and all packing out of course but either you tell me how to fix this or I want a replacement. I don't want money back, I want a working Litter Robot! My cats love it and I love the night light for them. This is heartbreaking for us. Isn't there a serial number on he unit where you could trace it back to the point of sale for validation?