Version PRO II of the RZ67 features a delicate fine-focus knob that operates through a gear reducer (this one). It is quite fragile and prone to breaking easily, resulting in a grinding sensation while adjusting the camera's focus.

This serves as a replacement for the gear. Printed at the highest quality settings supported by your printer, I used PLA and the "0.08mm Extra Fine" preset on Bambu X1C.

This is a good guide on how to replace the gear: https://www.youtube.com/watch?v=9ajQZa6_WQs