  Despite the supposed simplicity of double-closed shell nuclei, conventional
coupled-channels calculations, that include all of the known collective states
of the target and projectile, give a poor fit to the fusion cross section for
the $^{16}$O + $^{208}$Pb system. The discrepancies are highlighted through the
experimental barrier distribution and logarithmic derivative, that are both
well defined by the precise experimental fusion data available. In order to
broaden our search for possible causes for this anomaly, we revisit this system
and include in our calculations a large number of non-collective states of the
target, whose spin, parity, excitation energy and deformation paramter are
known from high-precision proton inelastic-scattering measurements. Although
the new coupled-channels calculations modify the barrier distribution, the
disagreemnt with experiment remains both for fusion and for quasi-elastic (QE)
scattering. We find that the Q-value distributions for large-angle QE
scattering become rapidly more important as the incident energy increases,
reflecting the trend of the experimental data. The mass-number dependence of
the non-collective excitations is discussed.
