  We report an analytical and numerical investigation into the impact of
helicity inversion in LHC processes that do not conserve lepton number $(L)$.
As a case study, we focus on the production and decay of Majorana neutrinos
$(N)$ through on- and off-shell $W$ bosons in the Phenomenological Type I
Seesaw model. Using the Monte Carlo event generator \texttt{MadGraph5\_aMC@NLO}
in conjunction with the \texttt{HeavyN} model libraries, we perform exact
matrix element (ME) computations without the narrow width approximation.
Despite helicity inversion appearing explicitly in MEs, we report the absence
of helicity suppression of $L$-violating collider observables for $1\to4$ and
$2\to4$ processes that are dominated by resonant $N$ production. We attribute
this incongruity to the different scalings of 4-momenta and squared 4-momenta
in MEs and squared MEs, with exact cancelations occurring in the latter when
$N$ goes on-shell in the small-width limit. In off-shell regimes, total
suppression / enhancement of $L$ violation can emerge. Implications for other
neutrino mass models are discussed.
