For example with the text 'the dog and the cat and the goat', if you open the search bar and search forward, it finds all three 'the' matches but if you search backward, it misses the first 'the'. Need to investigate why.
Related: Bug 10999
Hopefully fixed in http://git.xfce.org/apps/mousepad/commit/?id=9bc9d7853220163038d45e0a66be6048cc9f2449.