what is your encoder and pitch set to?
try pitch of 18 and encoder of 5400
the true pitch is 2mm with encoder of 600, but it’s slow due to firmware settings. multiply both to speed it up, but if you multiply too much over 9.5x the motor won’t be fast enough to execute the commands.
this thread goes into detail.
these settings only apply to your setup, other kits we sell have differnet z axis pitch or gearing.