I’ve studied this problem using a simple test pattern, and here’s what I’ve found:
- Pads or traces closer then 0.2" of the left or right edges (as defined by the “Material Size” CC settings) will shift the plot left or right.
- (I’m not sure exactly what this critical distance is; 0.15" causes a shift, 0.20" does not.)
- The drill file holes are shifted as well so at least the holes/pads still are aligned.
- There is no similar behavior with the vertical axis.
- This only occurs on the bottom layer (mirroring).
- If I have a close element on the left, I can place a dummy pad or trace an equal distance from the right edge and there is no shift.
I like using Carbide Copper for simple prototyping and lab gadgets. Now that I know what causes this behavior at least I can compensate for it, but it would be nice to have this bug fixed.