Circles Cut as OVALS, Consumables that are flat worn out!
In the illustration above, I have an exaggerated example of what happens when your consumables are flat worn out and why small holes .
When you create tool paths, the cad software assumes the cutting diameter (Kerf in plasma terms) is truly round. The trouble is, the kerf is rarely round... So what ends up happening is the cut actually deviates from the contour that its supposed to reflect.
The illustration on the right demonstrates what really happens during the cut. The small dashed circle is the tool path that the cad software generated using half the diameter of the Kerf. So as the "Real-World" Kerf (illustrated as an ellipse) rotates around the tool path while maintaining the same orientation (just like it would in the machine) over-cuts and results in a cut that deviates from the contour its supposed to match.