This is exactly what I found. See the posting Neutron capture gamma ray spectrum from Ni60-ceases to agree with NNDC database going from Geant4 v10.7.2 to v11.2.2 . It is important to note that the choice of ParticleHP parameter settings is critical to the resulting spectrum for both Geant4 versions and that results from one version can differ from the other for the same parameter settings.