Ok, I decided to take apart, clean, and move the troublesome y-axis rail. I soaked the slider and its ball bearings in oil for several minutes. It was a pain to get back together, but it seems to slide smoothly. I switched it with the x-axis rail. So far, I have heard no more unusual sounds. That said, there still seems to be a minor layer shifting issue. Basically, one layer will be a mm or two out of place.
I have upped the voltage on the stepper driver as high as it will go. I also have the belt tensioners on the y-axis belts. It just has these slight, one to two layer offsets. With it being more pronounced in the -y direction. No noticeable distortions in the x-axis. There are occasionally slight shifts in the +y direction, but they are relatively rare. ~20 -y ; ~4 +y
I am pretty sure the z-axis is fine, at least as far as the steps/mm. the 20mm calibration cube I printed came out exactly 20 mm in the z-axis. Though, it could be a height issue, since it mostly shows up with taller items. Now, the x and y-axis are another matter. They seem to be a little short of 20mm, though the y-axis seems to be the main one coming up a bit short. I can provide exact numbers and pictures after I wake up.
Also, based on Dustin's advice, I lowered the acceleration. It "may" have made a difference, but not much. it is printing the vases in vase mode, so there are not many quick movements.
What would you suggest?
