Printer after Board swap printing scewed/not square

Hi,
ive been working on a SKR1.3 conversion on my Malyan M300/Monoprice Mini delta for a long while now. I've struggled for months now on getting it to print straight,as you can see in the attachments, i can not seem to find the cause, i redid the firmware twenty times, ive run endless G33 Autocalibrations and had it apart a few times again. I can not diagnose the issue at all. I replaced the original endstops with new ones on printed mounts, i level using a foil switch on the nozzle, "Lerdge probe".

The first layer goes done fine most of the time but the scew always comes after the first few layers, even very small parts in the middle of the bed show that.

My G33 output:Calibration OK rolling back.
.Height:112.90 Ex:-0.65 Ey:-1.90 Ez:0.00 Radius:62.44
. Tx:-0.47 Ty:+0.07 Tz:+0.40

I measured the towers with a square to the table and they all are straight.

I run the latest marlin 2.1.1 with these configs:Configuration_adv.hConfiguration.h

I do hope someone on here has more ideas than me

The only reason I can think of is that the towers are not perpendicular to the bed. This leads to significant X,Y and also Z coordinate error. The Z errors might have been partially mitigated at the bed level by the calibration. But the higher up the printer moves the more tower positions are wrong leading the the part being skewed in all axes (X,Y and Z). You can check that the Z error is there as well by measuring the printed part height at different (X,Y) positions.
But you said that your towers are square. Though I do not know. That was the most likely reason for the error. Let us know when you find out.

Rotated towers can lead also to a significant distortion but that is mostly in (X,Y) plane and independent of the height. Therefore this is not a likely problem of yours.
Twisted towers (like corkscrew) can lead to the problem you have as well. But this is not a common error in a printer.

If some stepper skips steps occasionally then you can get the error you are seeing as well. Set the stepper current as high as your drivers and motors can handle (typically around 1.3 A). If a stepper skips a step at a such a high current level then it will by accompanied by a loud "click" sound.

If you are desperate and you are not afraid of math then check out this: [github.com]

Good luck!

Herceck, i took apart the printer and found a pulley that wasnt sitting perfectly on the shaft, seems like it might have allowed for some slipping or was causing some binding and reseating that seemed to have fixed the issue, i cant believe that escaped me for so long!

Right, a loose pulley definitely can be the reason.