rsync doesn't copy everything

Hi experts,

Scenario: 2 debian sarge boxes running this command each night: rsync -avPl -e 'ssh -i /root/.ssh/nas2_id_dsa' --delete --force --exclude '/some/obscure/path' root@nas1:/some/path/ /some/path/. Only one server is sync'ing with stratum 2 time server; the other does not sync with time servers.

Problem: Using comparison software (Beyond Compare), I see that not all files copy over--e.g. /some/path/directory/abc.pdf (though I've seen word docs and excel docs too) from NAS1 to NAS2--i.e. they are "missing" on NAS2.

Question: How do I make rsync copy everything over, or at least learn what failed?

Thanks!