The Zim Zeepro is a fun little printer, but the designers took a few shortcuts that can be annoying. One of those shortcuts is not doing a better job of securing the 6 mm shafts that the carriage rides on. Over time, they can push themselves through the support blocks and jam the mechanism. (I didn't take the mechanism apart, but I think they are just held in by prayers and good wishes.)

I printed a couple of bushings for each shaft, held together by M2x8 screws and nuts (although in my particular print, the holes threaded to the screws just fine and I didn't need the nuts at all).

Just install 1 bushing at each end of each rod to prevent it from sliding and you're good to go.