I finally manage to repair the archive ! I've
browse the code to determine where it's failing. I add some
debug log for my self to determine where the error was coming
from. It look like recovery was failing because some
"increments" file was left over by failed backup. I've search
them and delete them.
This might be something to add to your script. Basically,
when trying to restore 2015-08-21T01:12:31-04:00,
we need to delete every newer file from increments
directory. Then --check-destination-dir is working.