Reflow & Replace SMC
Remember that your troubleshooting steps should point to this as a potential solution, don't do this without a specific reason.
Remove edge bonding and heat at 280 Celsius with flux to burn any crap underneath. If no change, 430 full air flow no nozzle. Give it a light nudge once you can see it moving under the air.
430 full air, no nozzle. Grab it off once it is moving. Clean the board and remove all the old solder.
Mount your SMC upside down (ball side up) in a bracket/vice/clamp etc that will hold it still. Clean off the solder and clean with iso. Place your SMC stencil and hold it in place with tape or another method.
Apply solder paste. I use the back of a spudger to scrape the paste into all the holes. Go over it a few times with the excess paste to make sure the holes are filled. Brush the top clean with a dry cloth or iso pad (not soaked though). Make sure there isn't any excess paste sitting on top of the stencil.
Be PATIENT. I slowly heat at 385 degrees with airflow of 40-50. Hold it a few inches away to let it heat (I count to 10 or 15), then move it closer by an inch, count again. Keep doing this until you see the paste starting to heat and form balls. Don't get too close or you risk blowing the balls out of their holes. Again, be patient. Once all the balls are melted, inspect closely to ensure they are all similar and uniform. If any "bulge", push the solder down with the tip of your tweezer, and then heat it again until it melts and goes to where it should be. If any look small/low, add the tiniest amount of paste using the tip of your tweezer, and reflow.
As is it cooling, add a TINY bit of flux which will get between the stencil and the SMC to help with removal. This may not be necessary, but I find it helps.
Remove your stencil/SMC from your mount. I use a flat blade xacto and slowly wedge it under the edge of the SMC. Wiggle ever so slowly until it breaks free from the stencil.
Apply a small amount of flux to the board, and cover the whole SMC area. Not too much, or the SMC will "float" and might now stick to the right spot.
Apply the SMC into place, and again, slowly apply heat (low airflow so it doesn't blow away). You can hold it in it's place with tweezers, just be careful not to be apply pressure. Just keep it from moving out of place. Once it has attached itself in place, you can turn up the airflow to make sure it is properly flowed. I've found you can't go too high with the heat or airflow after a reball as the low melting point of the paste/solder will cause it to blow away, so just be aware.