Best posts made by spudaddict

@spudaddict OK, so smoking gun found. I went to swap out the other stepper motor and noticed three case screws (on the bottom) were missing. I replace the screws and two stripped out and two were loose. I pulled the T20 driver gear off, and there is grease speckled underneath.

So, I am guessing without the case screws the internal bearings got skewed and that the motor is likely unrecoverable.

I tapped the motor case and got 2 screws to hold - luckily they are diagonally opposite each other. Just for grins I started my "tube test" design as 3 of the 4 tubes consistently turn out terrible. Here is what I got:

Comparatively perfect minus some relatively minor tuning.

New stepper motor is on order and this is one to put in the troubleshooting books - if you ever get a repeatable bi-stable layer shift on a 45degree angle, check your stepper motor.

THANK YOU everyone for your input. I am implementing pretty much every suggestion I got as there are definitely other items that I can improve on. The improved belt alignment and stiffer front plane has been integrated into my new print head design. (and now I can even print it!!) Other improvements will continue. Thanks again - especially JamesM, mrehorstdmd, Danal who stuck it out to the end.

@Haggan90
Its mechanically interesting that your wall variations match each other on the x face and the y face. Do the indents and outdents match each other on the positive and negative x face as well? In other words, if you turn your cube to see the side profile of both X walls, do the indents look like

\ \
/ /
\ \ indicating some kind of wobble

OR

\ /
/ \
\ / indicating some kind of compression or extrusion issue

What kind of lead screws are you using and at what pitch?

What is the infill % and type you used on this print?

What power setting do you have on your Z stepper motors?

Are you using bed mesh leveling and have you updated it recently?