Sometimes when I am viewing changes, the GUI shows that the whole file has changed. I think this happens with the fix-quotes filter (but may happen with others). It shows at the top:
"Comparing sample to the filtered sample: 2999 lines added, 3000 lines removed, and 0 lines changed."
so I think only one line has changed. However I cannot see which line because the GUI shows that the entire file was deleted and replaced.