Hello I think i understand what Combo said and putted it to the test. In fact, when you make a match next to the sheep and it makes the bucket spill water everywhere, the sheep wont move, if the bucket is not full, the match will work and the sheep will move. (so it is useful to use a shovel to hit the bucket when it is…
It happened to me too on level 814 and now on 815, (still stuck on it) the black sheep wont move even if i make a match next to him....sometimes it does, but mostly not.. this is frustrating :-(