I had quite a lot backlash in the bronze tube bearings. Firstly I replaced the (shorter) top bearing for a bottom bearing, which is longer.
Secondly I replaced the rods. This was because I made my Vertex larger so I had to have longer rods. Fortunately this new rods were slighly thicker than the old ones and so, as a side effect, the bearings fitted precisely around the rods. I don’t have any backlash in the printhead anymore.
The only rattle I still hear is the radial fan on top when the head moves fast in x-direction. I once replaced that one also and that helped a little, but if anyone found a radial fan without the axis backlash, thus silent, I would like to hear…