Propagation of nonlinear coupled drift ion acoustic shock wave is investigated in an electron–positron-ion (epi) plasma in the presence of fully degenerate adiabatically trapped electrons. A novel complex nonlinear equation with fractional nonlinear terms is formulated. Phase plane theory of planar dynamical system is employed to investigate this nonlinear equation of epi plasma. The variations in nonlinear periodic orbits (NPO), nonlinear heteroclinic orbits (NHO), time series plots and shock profiles are demonstrated by varying the values of different controlling parameters such as the ratio of positron to electron number density, collisional frequency, magnetic field, drift velocity and angle of propagation. It is seen that a pair of shock structures are obtained – which is the most significant result of this work.