[Bad layers at specific z-axis range]

I unplugged the power and moved the platform physically up and down a few times. After this, I printed the cylinder.

For scale, the cylinder is 20mm in diameter and 40mm in height.

What could it be...

[Bad layers at specific z-axis range]

It also could be the ball races on the Z pillars, I had a suspect one.

Do you hear anything odd when you do a Buildplate up/down?

 

Nothing when it moves up, but on the way down I hear soft clicking sounds. I read in some topic that this is isn't anything to worry about.

[Bad layers at specific z-axis range]

Thanks for the reply gr5

I've taken some better photos with a better camera:

Does this help to tell what the issue is?

[Bad layers at specific z-axis range]

Hi there! I've had a blast with my Ultimaker 2 GO. Finest piece of equipment i own!

I've mostly printed flat or small parts so I haven't really noticed the issue until now. More often than not, I get stripes within a specific z range. Not completely broken layers, but it seems like the z-axis steps the wrong height - i get both thin layers as well as fat layers.

I can see a small scratch in the z-screw, I suspect that could be the cause. The placement of the scratch also makes sense for where the bad layers appears.

What do you suggest I do here? Where can I find a replacement for this piece? Could there in fact be another cause of this problem?

Thanks in advance!