  Fe doping in Ni$_2$Mn$_{1.5}$In$_{0.5}$ results in suppression of the
martensitic phase via two contrasting routes. In
Ni$_2$Mn$_{1.5-x}$Fe$_{x}$In$_{0.5}$, the martensitic phase is converted to a
strain glassy phase, while in Ni$_{2-y}$Fe$_y$Mn$_{1.5}$In$_{0.5}$, a cubic
ferromagnetic phase results at the expense of the martensite. Careful studies
of magnetic and structural properties reveal the presence of the impurity
$\gamma -$(Fe,Ni) phase as the reason for the emergence of non-ergodic strain
glassy phase when Fe is sought to be doped at Y/Z (Mn) sites of X$_2$YZ Heusler
alloy. Whereas attempts to dope Fe in the X (Ni) sublattice result in an A2
type antisite disorder that promotes a ferromagnetic ground state.
