Help! For some reason my Z-axis is multiplied by 10.

Just assembled my first 3d printer and after some teething problems I got the first layer working correctly. However each subsequent layer instead of going up by 0.2mm the Z-axis raises by about 2mm.

Steps per mm are configured correctly at 2560 and jumpers are installed correctly. When modified to 256 steps per mm movement is correct but homing speed drops dramatically.

The printer I have is a Geeetech I3, full aluminium.

I would prefer not to reflash any firmware since it looks a bit complicated and I don't want to brick anything, but I will if I have to. Anybody got any ideas?