  We report on the effects of 3.5 MeV proton irradiation in
RbCa$_2$Fe$_4$As$_4$F$_2$, an iron-based superconductor with unusual properties
in between those of the pnictides and of the cuprate high-temperature
superconductors. We studied how structural disorder introduced by ion
bombardment affects the critical temperature, superfluid density and gap values
by combining a coplanar waveguide resonator technique, electric transport
measurements and point-contact Andreev-reflection spectroscopy. We find an
unusually weak dependence of the superconducting properties on the amount of
disorder in this material when compared to other iron-based superconductors
under comparable irradiation conditions. The nodal multigap state exhibited by
pristine RbCa$_2$Fe$_4$As$_4$F$_2$ is also robust against proton irradiation,
with a two-band $d-d$ model being the one that best fits the experimental data.
