Long Nb-NbO-Pb Josephson junctions with artificially formed SiO inhomogeneities in the insulator layer have been studied. A fine structure has been observed on the current-voltage characteristics of the junctions. Such structure is considered to be due to the resonant interaction between the fluxon and its radiation. The single-fluxon effect in the zero magnetic field and the multifluxon effect in a large field have been studied experimentally. The results are compared with those of the perturbation theory and numerical simulation. A multifluxon-chain pinning effect observed in the commensurable lattice of inhomogeneities is reported and discussed.