Smbclient exits with code 1 if the last download failed. This commonly happens for non-existing GPOs, which is fine and expected, though. 

2017-07-10T14:07:28.014082+00:00 ERR authpolicyd[4172]: smbclient failed with exit code 1

Suggested workaround: Do some dummy operation in the end (noop? cd to some dir) that resets the exit code.