Z-axis skips threads

Hi there.

I’ve had my K8200 for about 2 months now and since the day I put it together I have noticed a problem that is causing me to re calibrate the printer after every use.
When the Z axis is raised above around 5-10cm when you send the axis back down it starts to skip threads and causes the calibration to go all over the place and the nozzle ends up a few mm lower than it should be. What can I do?