It need not be perfect semicircle as in debye relaxation. It can be stretched semicircle or more than one semicircle depending on number of relaxation process in your sample. By the way the Cole Cole plot doesn't look proper.

Tarun Yadav

Maybe this article will help you

Article Hydration of tetraalkylammonium salts

For non-Debye type relaxations, the semicircle will be depressed in nature. Additionally, there could be multiple semicircles for different electrical entities having different resistivity. Moreover, electrode polarization effect can bring an extra tail, which may be a distorted semicircle or curve.