Strange z axis ticking
I am using a Prusa I3 Mk2 upgraded clone with Ramps 1.4, A8994 drivers and Mattercontrol.
Recently, after printing perfectly for days, the z axis has started ticking and slowly moving upwards before a print. This only happens between pressing the print button and the hotend moving to its print position.
I have tried:
1. Swapping drivers
2. Setting a lower Vref
3. Checking ease of movement of screw threads
The result is a random Z offset and prints not adhering to the bed.
This does not occur if I export the gcode file to SDram and insert it into the printer. It prints normally
Anyone had the same?