Brake pad kickback when apply brake with sound and getting no brake, jst slip a on 2003 Toyota Camry

My car has brake problem. Some times on non paved roadswith a speed of 2mph the brake pedal kick back with a vibration to the pedal and a sound comes. The same things happens when you drive on ashphalt roads and a sudden brake application. Is this any relation with ABS or sensor. I changed the master cylinder and all the discs,front and rear but no change. I even adjusted the wheen disc in a lathe since the mechanic told that it has got bend.But when we ump the brake there will not be any problem but sometimes the brake slips irrespective of the speed. Please help me

Asked by for the 2003 Toyota Camry
Have system scanned for TROUBLE codes!! Light on?
3 more answers , 3 more comments
Damaged or broken reluctor ring??
Or wire/connector @ wheel speed sensor! Scanner find it every time, while driving, but light most of the time will come on.
no light comes, will the light flash when the ABS activate??????????
the ones I'm familiar with do.
Could be a normal thing if you brake hard on a gravel, wet grass, or slick road. The ABS system kicks in when it senses a wheel that may be sliding on pavment. Likely there is nothing wrong.
review when brake fluid was flushed last. could be due if not enough pressure to activate. it could also be a problem with the calipers. ask mechanic if there were any problems releasing the calipers. gravel roads always hard on calipers. worst case is it could be a collapsed brake line. ask mechanic about calipers first.