I'm out of options; rear part of prints always "scratchy" and uneven  

I'm out of options; rear part of prints always "scratchy" and uneven

Hello,

Our Mk3S with MM unit2 want printing unacceptable from one day on the other, out of the blue.

It doesnt matter on which part of the printbed i print, the rear last 10mm is always "bad". I cant think of what can cause this.

From all the prints i make, the front left and right are really perfect. The rear is always ugly. Side is looking as the layers are not straight above eachother and look "wavy".

The top looks very unsmooth. The printnozzle also scratches on the print over thhre, always approx. the last 10 millimeters of the print. The higher it is, the worse it gets.

Tried many things, but i cant think of anything that can cause this.

Its not the whole print, so it cant be spindles, of uneven bed. Print doesnt come up, bottom is sticky and flat.

The rear has "threads" when coled down, you can literally "pull" a "molten wire" print from the rear. I think this is due the printhead whobbling front to back with scratching the bottom. if i wouldn't know better, i'd say the printhead is too low printing the last 10mm of a print, compressing the material too much. But that wouldn't make any sense...

First layer is good.

bearings replaced, same results.

Belts tensioned, same results.

Printing with octoprint or SD same results.

Printed "older" designs that went perfect before, same (bad) results.

Anyone?