I've only used it a couple of times trying to make fries, can't remember what else I've ran through it but not much. I thought it'd be good for salsa so I still plan on trying that.
I have a stack of placemat sized cutting boards (thin plastic sheets) that I pull out & use on my counter or built in cutting board...easy to clean, & it just works for me. I'm sure the unit isn't defective. Everything fits nicely, I can see how it works. I've even tried to cube using the wider teeth & slicing perpendicular to the way they'd run...
Maybe they're just not made for potatos. I really have no idea on how to use it. Maybe I should watch a youtube video or two.