You said you took a file to clean but not to bare metal. I live where they salt the roads and rust and corrosion are prevelant. It is sometimes hard to tell if they are cleaned well. Most of the time when I use a wire wheel I can make it look really clean but it turns out it’s not. Use your file or the edge of a cut off wheel to get it to shiney metal.everything the clip touches should be shiny. Use silicone brake lube on clips.pads should slide freely back and forth in bracket. I think you need to clean better.