Do you experience problems during downloading?
Check your connection in Status and Interface settings window.
Use Test Server in Config > Servers.
We will probably ask you to do a test using only basic settings.
Do you experience problems during repair or unpacking?
Enable +Debug logging in the Status and Interface settings window and share the relevant parts of the log here using [ code ] sections.
You probably forgot to mention these files are on some kind of network share or external disk. Which is apparently setup so that files are owned by uid 99 - which doesn't appear to exist on your system and therefore probably doesn't match the account running sab. And since nobody but root can change permissions on a file owned by someone else... sab will fail to change those permission if you tell it to do so anyway.