This free, standalone, exe flashes a borderless, configurable, area that will stay topmost while it's running. Drag it into place and then the only other configuration is an X,Y size input that is accessed by right clicking on the active area. You can even size it down to a single pixel (if you have the patience to interact with it). While running it flashes through RGB to hopefully loosen those dastardly stuck pixels.
Open an instance and size it to your trouble-spot. Set it and let it run...