rsync 3.0.7 - error deleting directory

[Philipp Herz - allied internet ag]

Hi,

based on a nightly cronjob we use "rsync --delete" to delete partitial 
directory structure from a backup folder. Sometimes rsync is unable to 
delete structure as told.

rsync: unlink "/backup/usr/lib/gcc/x86_64-linux-gnu/4.1.3" failed: Is a 
directory (21)
rsync error: some files/attrs were not transferred (see previous errors) 
(code 23) at main.c(1042) [sender=3.0.7]

Please let me know if there are any known reasons for this behavior.

Regards - Philipp