Are your z smooth rods loose? All smooth rods of a printer must be well fixated to ensure good print quality. My printer has just holes for the rods which have non-zero clearance, they can move around a bit in the hole. These clamps fixate the z rods by pulling them to the front.

These clamps probably won't fit your printer but take it as a design inspiration. You need two 20mm M3 screws and two M3 nuts. These clamps are for rods with a diameter of 8mm.