2014 Ford Taurus - Brake issues

Brake problems. 63,000 miles, time to replace brake pads normally but theres a lot of highway miles. Thing is right rear brakehas been sticking on and my wife tells me that she has smelled this before. Just like tires out of balance, there are signs of what is happening with the way rotor bad. This is ground up on the outside instead of the inside of the right rear. Any help will be appreciated. I have the aftermarket warranty from the dealer but I might not get an answer from them what causes it. others are ok. Sounds like the caliper froze up butt I have always seen the inside worn and this one is not. Can’t fell the pedal pulsating like the rotor is warpped. Just never had this particular thing happen before.

Things break or just wear out and there might not be a obvious reason for it . Most places will just fix it and not waste the time to find out why. Also I doubt if your extended warranty will cover brakes as they are called a wear item . But you can ask before you have them do the work.