Problem with the brakes (possibly quite common)
 

Found out the brake pads get stuck inside the caliper and don't slide normally when the brakes are depressed. The brakes don't have enough braking power, the front wheels get hot, the brake pads wear out quickly, and emergency braking at higher speeds can get hazardous. Have a look at this video

You know what the issue is??
The caliper bracket, which holds the pads, needs to be cleaned properly and new brake hardware installed
The caliper itself needs to be inspected. Don't forget to check the slide/guide pins for free movement.
They sometimes get frozen/rusted.

Thanks, I've cleaned all parts, and greased the guide pins along. It seems to me the tolerance between the pads 'legs' and their groove into the caliper bracket (where the shims sit) it very very small, with time the pad legs rust and swollen a little bit and this seems enough to get them stuck on the bracket. I've cleaned near these pad legs but they were still getting stuck, so in the end I just sanded down a little bit these pad legs to remove some material.

The bracket, where the stainless steel shims sit, needs to be cleaned properly.
Remove all the rust. Then brake grease is applied to the bracket before the shims.
The grease is suppose to keep the rust build up to a minimum.

If you're interested there is a good video

I recently worked on the brakes of our '08 Sonata. What I noticed is that the brackets that hold the pads have a factory coating on it. One pad in the rear was stuck so bad it crumpled when I tried to pry it out. Brushing, sanding and filing was not effective in creating a good clearance for the hardware and pads. In the end I chipped off the factory coating, filed the metal clean and used caliper grease on the exposed metal. I had the rotors resurfaced and used new pads and hardware. I also completely flushed the brake fluid. Since then the brakes perform flawlessly.

Thanks for the update.
Hope this fixes your brake issue.

A lot of people doing brake work don't realize how critical it is to remove the caliper slide pins , clean them inside and out thoroughly and use only synthetic grease because other greases attack the rubber boots.

Also , rust build up on the caliper where the pads move and are retained must be removed so the pads are free to slide. I found putting any type lubricant in those slots only attracts dirt and builds up to where it jams the pads and there is plenty of dust and dirt that gets in there.
Careful clean work pays off do it right and do it once !