  The rapid neutron-capture process ($r$-process) has for the first time been
confirmed to take place in a neutron-star merger event. A detailed
understanding of the rapid neutron-capture process is one of the holy grails in
nuclear astrophysics. In this work we investigate one aspect of the $r$-process
modelling: uncertainties in radiative neutron-capture cross sections and
astrophysical reaction rates for isotopes of the elements Fe, Co, Ni, Cu, Zn,
Ga, Ge, As, and Se. In particular, we study deviations from standard libraries
used for astrophysics, and the influence of a very-low $\gamma$-energy
enhancement in the average, reduced $\gamma$-decay probability on the
($n,\gamma$) rates. We find that the intrinsic uncertainties are in some cases
extremely large, and that the low-energy enhancement, if present in
neutron-rich nuclei, may increase the neutron-capture reaction rate
significantly.
