RotamerPackeer rotamer space enumeration and single pruning is working as expected.  There is a bug in SidechainMutator in that it ignores the expected immutability of the connectivity graph.  When it gets to proline, it disconnects the chi3 bond to the backbone but doesn't put it back.  I don't think this has any real effect, so I'm ignoring it.  The only thing I did is turn off the warning of finding a null edge when mutating to a proline in SidechainMutator.