Make sure you have removed the original lead screw covers as specified in the preflight check and disassembly guide

This is not optional, the original lead screw covers are not compatible with the Bear Z motor mounts.

Screw the Bear z_leadscrew_caps on both motors.

The z_leadscrew_caps should screw down to the Z motor but should not be tight at all. Make sure the lead screw can turn freely.