Make sure the both Z motor cable has the same orientation in the motherboard (same order of cable colors also), if the 2 motors don’t work together,it means the motor driver doesn’t have enough power for the 2 motors adjust the small potentiometer to give it more current:

https://www.youtube.com/watch?v=GNfKZ7o_7PI

One more thing, if you have heat sinks for the driver install them now , and prepare a Fan witch will cool the drivers.

It was an easier fault. The z axis isent straight. It wobbles like there i no tomorrow… Will get new onces. Thanx for the help