Couple things I see that I would address that may or may not be contributing to things.
First is the backing plates look a bit off center. That could bind up on the slide pins and not allow proper movement of the pads. Perhaps keeping them in contact with the brake disc.
Maybe remove those backing plates and try it again. I had a similar thing with the rear pads on my '07. Removed the backing plate and all was sorted.
Second, get you an old toothbrush and clean around those caliper pistons. All sides, top and bottoms. Also the flat area where the brake pads sit. Then give the lever a small squeeze to push the pistons out just a bit more. If you're worried the pistons may pop out, put the brakes pads between during that small movement.
That will expose another circle of brake dust, grime, etc. Give the pistons another brush away with ye olde toothbrush then press the pistons back in. One more final brush then put the pads in and reassemble.