First layer issue
Hello !
I bought my MINI about a year ago and did quite a lot of successful prints in the first months. Then I did have any time and re-started using it a few weeks ago. It seems like I now have a lot of prints that unstick - I’ve tried cleaning the bed, but it didn’t work, most prints fail.
so I got to first level calibration to adjust Z-Level, and there I notice something very weird : I think my z-level is okay because the rectangle is like in the manual pictures, but when it does the straight lines, they are perfect when going left to right, but they have small ripples when going right to left… 
I thought it might be a nozzle issue so I did two cold pulls, but the result is the same. Any idea ?
very thankful for any help as this is becoming a little frustrating 🙁
cheers
Valentin
RE: First layer issue
Your z level is still too high, nozzle should be closer to the bed.
You can see that the filament is not squished between bed and a nozzle when extruding.
See https://www.printables.com/model/107639-first-layer-calibration-prusa-mini
See my GitHub and printables.com for some 3d stuff that you may like.
RE: First layer issue
Printer also isn’t square. You can see that the lines are even in one direction and wavy in the other leading to uneven extrusion.