Sounds like brake disc is making contact with pad shims

I’ve been having trouble with a noise from the front left brakes on my 2003 Yaris/Echo/Vitz/Platz. The car takes a beating but is also well maintained.

After a long drive with repeated hard braking or a few minutes out on the track, I can hear a grinding sound when brakes are applied lightly at slow speed.

So far, I have replaced the following in an attempt to fix this:

• Performance discs
• Normal quality aftermarket discs
• Fast road pads
• Normal quality aftermarket pads
• Brake shims
• Slide pins, grease, rubber boots

Each time I dismantled it to swap a component, I removed the pins, cleaned out the bore with brake clean and a narrow long brush and added a thin coat of ceramic brake grease for the pins, and copper grease for pad/shim/caliper contact.

I also, sprayed down the hub face with brake clean and applied some copper anti seize to that area.

I can’t see any obvious sign that the disc is making contact with anything, there are a few marks that I am suspicious of, but can’t say for sure.

Another test I have done, is fit the pads WITHOUT the shims. With this set up, the pads rattle, but grinding noise goes away. So I think the disc is hitting the shims. Given that I have replaced the shims, what parts should I throw at it next?

Update: here is how it sounds: https://www.youtube.com/watch?v=7m9RyuOVBOc

Update: Is it possible that the wheel bearing / hub assembly is offset and causing the disc to sit close to the caliper than it should?

Update Jan 2017: I have replaced the caliper and the caliper bracket with a used unit. I used the shims that came with this old caliper. It appears the problem has resolved but I will wait for a while before confirming.
I have a theory that the shape of the mounting bracket or caliper was damaged when the previous owner painted them red. I currently have 3 red calipers and a single unpainted one, perhaps I will replace all of them with unpainted used ones at some point.

Update Feb 2017: The noise has returned, it’s less pronounced than before, but its the same noise and can be felt through the brake pedal. As before, it only occurs after hard or extended driving.

Update July 2017: Its stopped making the noise. My guess is, it will return once I replace the pads or remove/refit the caliper at some point. Its just “seized” in there and found its happy place, or some kind of mystery.