A Google Web Search Help thread has confirmed reports of a bug with Google Search and the next page button.
When you get to page three of the results, the results continue to repeat themselves.
For example, you click next from page one to page two and then from page two to page three and it works fine. But when you try to go to page four, it cycles you back to page three. You can reproduce it yourself for the search phrase [MAFPS flight planning].
Here is a video:
This is not the first time we've seen this bug. We reported a similar issue in 2009.
Googler Sarah responded saying, "Thanks for reporting this. I could see the same thing and we are investigating now."
Forum discussion at Google Web Search Help.