my guess is the brake pad sliding around in the caliper.

honda had a tsb about this 10 or so years ago on the elements.

brake pad has too much clearance side to side in the caliper due to a faulty clip, and clicks in forward and reverse as the pad moves about in the caliper. same should apply to any vehicle that has a similar clearance issue...

deal with it, or replace the anti rattle clips and brake pads was honda's fix... may want to have a look at your brakes...