Eraser brush edge not sharp

The edges of my eraser brush are sharp at 100% hardness, but as the edge gets softer the edge of my brush gets diffused/pixilated. It makes it very hard to follow the edge of an image since the brush edge isn't sharp and it doesn't start to erase till the middle of the diameter of the circle. I attach a sample of the brush edge at 0% hardness, showing where it starts to erase. I tried resetting the tool and have futzed with the brush settings. Nothing seems to work. This just started happening.