Just read that if during the first audit gives them reason to think an error might have been repeated over the years, then you're likely to get a second one. Perhaps a third.
Read that truly random odds (i.e. nothing that causes them to think something is wrong) are about 1%. So, if nothing turned up in the first one, the odds of twice randomly would be 1 in 10,000.
It's the error in the first that is triggering the second....seems to me.