  The physics goals of NOvA are the constraints of neutrino oscillation
parameters such as the octant of $\theta_{23}$, $\delta_{\rm{CP}}$, and the
neutrino mass hierarchy via a joint fit to $\nu_{\mu}$ and $\nu_{e}$
oscillation spectrum. We do this by propagating $\nu_{\mu}$ from the world's
most intense neutrino beam at Fermilab, over a baseline of 810 km to northern
Minnesota, USA, and measure the $\nu_{\mu}$ to $\nu_{e}$ oscillation
probability. NOvA announced its latest oscillation results, based on
8.85$\times10^{20}$ (6.9$\times10^{20}$) protons on target neutrino
(antineutrino) data. Preliminary results for the allowed values of oscillation
parameters are: $\Delta m^2_{32}=2.51^{+0.12}_{-0.08}\times 10^{-3}
\mathrm{eV}^2$, $\mathrm{sin}^2\theta_{23} = 0.58 \pm 0.03$ (upper octant), and
$\delta_{\rm{CP}}=0.17\pi$ with preference to the normal hierarchy. Reliable
constraints on these oscillation parameters require a rigorous treatment of
systematic uncertainties and thorough cross-checks. In this paper, we present
an overview of the treatment of systematic uncertainties as well as
cross-checks using muon removed simulations and cosmic muon bremsstrahlung
showers.
