I see this fairly often. The site appears at the same position on page 2 and sometimes page 3 as it does on page 1.
e.g. Position 3 also has position 13 and position 23....all the same identical root URL. It is always 10 places further down the SERPs, suggesting any switching of data centers when hitting next page or other technical explanation of flux isn't the cause.
I figured it was a Google glitch, and as it is most often my sites I notice this for decided not to complain ;)