Based on the answers provided, the following corrections need to be made to the 3D object:

1. Change the shape of the cutout to be semi-circular. Currently, the cutout is either triangular or trapezoidal, which does not meet the requirement.

2. Once the semi-circular cutout is created, ensure that the flat edge of the semi-circle is on the longer side of the rectangle.

3. Make sure that the semi-circle is negatively extruded to create a cutout in the original rectangular object. Currently, it's unclear if this is the case due to the incorrect shape of the cutout.