I was just checking for new pages being indexed from a specific directory using site:example.com/dir/sub-dir
Initially when I searched I got over 100 results.
I clicked on page 2 and got the same number of results at the top of the page. I clicked on page 3 and got no results found. So I started the search over and got no results found. I did a 10 sec. huh? Then searched again and got the original number. So I clicked on page 2 and got no results found. So I started the search over and got no results found.
I didn't ever change the initial query, so there's no way I searched for two different things. I just clicked the magnifying glass to start the search over when I got no results right after I had seen the initial number and pages they had indexed.
Anyway thought it was interesting you could hit different datasets or data centers with Bing any time, including going from page 1 to 2 or page 2 to 3 of the results.