  We examine the effects of Pt vacancies on the magnetotransport properties of
Weyl semimetal candidate GdPtSb films, grown by molecular beam epitaxy on
c-plane sapphire. Rutherford backscattering spectrometry (RBS) and x-ray
diffraction measurements suggest that phase pure GdPt$_{x}$Sb films can
accommodate up to $15\%$ Pt vacancies ($x=0.85$), which act as acceptors as
measured by Hall effect. Two classes of electrical transport behavior are
observed. Pt-deficient films display a metallic temperature dependent
resistivity (d$\rho$/dT$>$0). The longitudinal magnetoresistance (LMR, magnetic
field $\mathbf{B}$ parallel to electric field $\mathbf{E}$) is more negative
than transverse magnetoresistance (TMR, $\mathbf{B} \perp \mathbf{E}$),
consistent with the expected chiral anomaly for a Weyl semimetal. The
combination of Pt-vacancy disorder and doping away from the expected Weyl
nodes; however, suggests conductivity fluctuations may explain the negative LMR
rather than chiral anomaly. Samples closer to stoichiometry display the
opposite behavior: semiconductor-like resistivity (d$\rho$/dT$<$0) and more
negative transverse magnetoresistance than longitudinal magnetoresistance.
Hysteresis and other nonlinearities in the low field Hall effect and
magnetoresistance suggest that spin disorder scattering, and possible
topological Hall effect, may dominate the near stoichiometric samples. Our
findings highlight the complications of transport-based identification of Weyl
nodes, but point to possible topological spin textures in GdPtSb.
