Question on RAMBO and Z stepping

[RalphFerro]

Rambo on a MendelMax 1.5 prints correctly on x and y direction but does not step correctly on z axis. Hot end eventually crashes into the partially built model.

[NexusFlux]

First I'd check for mechanical issues. Make sure there is no binding in the X platform on the Z rods. The whole platform should ride smoothly from top to bottom with no chattering.