Hi Alex - I *think* i was getting some Z axis binding even though nudging using manual control seemed fine. Lubricate all the sliding surfaces and threads if you havent already. After that you might need to pull it apart and re-check everything. In my case i didnt know that the straightness of the threaded rods is a problem with the Geeetechs, and the threaded nut was a bit tight, as there was some material removed when i ran a tap through it.