I've seen the same results. I was thinking there was some awfully short timeout being set.
For me, it usually came after I spent some time studying a benchmark. It goes something like this: start a search, find a benchmark I want to look at and click on it, read-read-read, hit the back button, click on page 2 and get told there are no more responses. Restart the search, click on page 2, get a list, find a benchmark... etc