Ditto on this. I’m having issues of my own on a TAZ 5. Imperfect circles and line pairing(which I also see in the picture) are caused by the same issue; a delayed response in an axis when switching motion direction. The challenge is finding what’s causing the delay; resistance to motion in one axis, insufficient belt tension, slop in a carriage’s motion, too high of an acceleration value or too high of a jerk value, to name what I know of.
What I see in the picture suggests an issue in both X and Y, but more Y than X(assuming Y is vertical in the photo and X is horizontal).
First I had it happen on the X Axis and in my case what was happening was the X carriage was actually tilting parallell to the Y axis every time it switched directions. I had to move the linear bearing holders closer together(after reprinting a backplate due to faults on the original causing the bearing holders to move again as I itghtened the screws) to make it wiggle less. I also moved the X motor all the way down so the belt is kind of pulling down on the carriage. I had originally moved it so the belt was level because in my mind that hsould result in the most accurate motion.
Now I’m having it happen on the Y axis, and once again partially on the X axis, I think. Only on the Y axis I can’t seem to do anything that makes it go away. I’ve moved the linear rods around, I’ve moved the bearing holders around, I’ve tightened the holders bolts on one side while leaving the others loose, I’ve tightened the hell out of the Y belt, I’ve added white lithium grease to the rods, and STILL I am getting oblong circles with points at 11 and 5 o’clock.
At this point I’m very frustratingly out of ideas. For the OP on the other hand I’d start with tightening the belts. On the Y axis, loosen the motor mount and the idler bearing mount, then take the Y axis off the printer(I think that’s still possible on the 6) and flip it over to get to the clamp screws on the moving platform. Tighten the belt by two or three teeth, clamp is back down, then retighten the bolts on the motor mount and idler mount.
For the X axis on TAZ printers it’s not so easy. I’d recommend against loosening the set screws that hold the X ends onto the smooth rods. I did that and ended up with binding Z screws because I got them too close together. For this one just loosen the clamps on the X belt while holding the free end of the belt with pliers, pull it one or two teeth tighter, and retighten. Trickier than the Y axis.