I don’t have a picture (should have taken one when it was apart).
brass tube, an acetal nut on the bottom (with two screws clamping, not through it) attached to the clamp carrier assembly. Inside the tube is a spring, then another nut with wings keeping it from turning in the tube. It looks from the outside like a ballscrew nut, but it’s not.
These are representative parts below. I think the upper nut is correct, the lower in mine has a tube assembly, not just a aluminum plate, but it’s shown here the same way it’s attached to the carrier - “Pinched” by a couple screws clamping on the plastic.
Problem: Although the carriage can move up and down without observed backlash, if you grab the carriage, it doesn’t take much force to move it up and down ~ 2mm - looking closely, the threaded rod is moving up and down in the lower nut indicating that it’s either worn out, or has extraordinarily loose threads.
The machine has less that 20 hours on it with this Z, so to wear out that quickly seems ridiculous, and they basically want $30 for the acetal lower nut. You can buy a common all brass 8mm leadscrew nut for <$10.