Audits doesn’t check the whole data, only randomly selected pieces of the randomly selected segment. They are exist to help the satellite to make a decision, should it trust your node or not.
However, if it detects that more than 4% are not readable - your node will be disqualified, see a summary:
I can assume that some not readably pieces can be read after 3 attempts with 5 minutes timeout, otherwise your audit score would be affected.