I just found a bunch of black crud around the blades of my nutribullet. I unscrewed the little screws on the underside of the blades to try to clean it thoroughly and now I can't seem to screw them back securely. Can anyone help me out?

Huh. Maybe try calling customer service? A couple of people have discussed the "black crud" -- It hasn't happened to me yet, but I fear it's going to happen sooner or later..

I have actually been having the same issue over the last few months but mine has brown crud and smells like rust. I haven't called customer service yet but I need to.