Sabot moving too easily

This mower very well, is light and easy to use. Except for the hoof. One team this hoof trimmer. Is moved by pressing it a little louder than normal (the "notches" block the shoe in a given position). The only problem is that cutting my hair alone, I keep falling back to the shoe has the minimum length (no, I do not support strong). Hello accidents ... It maybe takes a particularly my lawnmower, since I do not see this comment in others. But this is definitely not practical.