I found that in PLA, a lot of the original parts are really easy to over tighten and crack. So I have been gradually replacing my parts with PETG (the cheap Microcenter Inland brand). My Z assembly is PETG with a bit of ABS. The PETG is far stronger than the PLA. All of my parts use 0.3mm layers.
Is that the Makita router or the Dewalt?