Background eraser not completely erasing??

For some reason, my background eraser won't erase everything I go over. In this picture, the character was wearing a necklace, and I was trying to erase the character except for her hat (not pictured). However, when I go over a spot, it dosen't completley erase it. As you can see, the shine of her necklace is still left behind. No matter how many times I go over it, it won't go away. Hardness is at 100%. I've tried playing with all the little buttons at the top, and still can't figure it out 😞 Thank you.