It seems like already known issue - http://www-geant4.kek.jp/lxr/source/processes/hadronic/models/neutron_hp/src/G4NeutronHPNXInelasticFS.cc#L52 but it is relevant for isotopes of Calcium, Lead and Co-58 because G4NDL4.5 has (n,x) data for them below 20 MeV.
*** This problem has been marked as a duplicate of problem 1789 ***