[CentOS] Mirroring CentOS problem.

I have two servers that, one time in a week, make a mirror o CentOS 
distribution, the mirroring come from two different italian servers but 
all the mirrors process stops with this message:

sent 267 bytes  received 374865 bytes  44133.18 bytes/sec
total size is 6472762072  speedup is 17254.63
rsync error: some files could not be transferred (code 23) at main.c(1146)

What's the problem?
Ps excuse me for my english.

Regards
Amedeo Fragai
S.C.A. S.r.l.