I too have suffered this fault. My solution thus far has been to add a second nylock nut onto the bolt. This second nut seems reasonably successful (see images below).
I’d also strongly suggest re-tightening and rechecking everything pretty frequently. Having had the eccentric nut/spacer come loose during a job, it’s now worn away the shoulder on the hole in the carriage upon which the spacer sits. WhileI was pulling things apart, I’ve also found that the two screws that clamp the Delrin nut were also just about to fall out,
