Hi! Thanks again for reporting the puzzle bug.
I've found and fixed it and will upload a new version now. The puzzle gained 5 more symbols each time you changed the difficulty on top of the previous ones, which could also produce duplicates.
BTW: The difficulty setting only affects the action parts. In the accessibility menu, there is an option "simplify puzzles" that will reduce the puzzle difficulty (e.g. reduce the number of symbols in this puzzle from 5 to 3).