Yes. Crack-Free NURBS requires more RAM and CPU speed to calculate the smoother polygons.
Here is your phone in standard NURBS mode. There is a problem with the symmetry. This can cause chamfering to not validate properly.
Here are the two cuts being made into the phone. The sphere and cylinder. I would try completing a cut from one of these first before attempting the next cut. Then doing a chamfer after both cuts have been made rather than inbetween each cut.