Can you post some more examples of bad placement. Being off more than 1/4" is isn’t right. Being off after calibration is definitely off.
Here is a topic I started for one of my machines that was skewed.
Using dead flat material and the Set Focus tool, do this image. You can use cardboard as long as it is very flat. Use hold down pins if necessary. Post before and after shots without having opened the lid of the lid camera image.
