Brake Grinding Noise on 1995 Disco

Decided to replace rear rotors and pads to eliminate a rubbing noise that sounded like a pad sitting against a rotor. I used the ProLine brand pads and rotors. After replacing I still have the rubbing noise, but now also have a terrible grinding noise. Everything has been checked for tightness and the pads are oriented correctly in the caliper housing. I can not figure out where this is coming from. The brakes don't make the rubbing or grinding sound when slightly depressed. They rub with when the brakes are not depressed. They make the grinding sound when under heavy braking right before the vehicle slows to a stop. I believe these are two separate issues. The rubbing could be a piston that's not retracting all the way and with new thick brake pads doesn't leave that much room. The grinding sounds like metal-on-metal, but has me completely puzzled.

Any thoughts?

Mud shield rubbing somewhere? Sticky caliper piston/pins? Loose wheel bearing?

Mud shields are not rubbing. I'll check the bearings but that shouldn't be the problem. I'm thinking I'll just replace the calipers. I appreciate your comments.

Problem solved. Amazingly, prior to completing the rear brake job there wasn't any grinding sound. After completing the rear brakes there is a grinding sound. Complete coincidence. Just so happens that the front right brake pads began eating into the rotor just as I was taking a test drive to ensure the back brakes had been installed correctly. Replaced the front rotors and pads and all is quiet.