2014 HONDA CRV

Hi. I have a 14' Honda CRV auto, 4cy. An issue started about a week ago
where everytime I push the brake at a stop sign there is a grinding noise
from the left rear tire. It only goes away if I set the parking brake, and then
release it. But then it's right back at the next stop. I've visually inspected the
right rear pad and it's still got about 70% left on it but the rotor is scored and
there is metal shavings from it. My question is what could be causing this
and how can it be fixed? Thank you.