When I've had this problem the rotor was a bit bent, and squeezing the brake just lightly touched it to the rotor evenly through its rotation which stopped the 'tsk tsk'. I realised when it occurred to me that the 'tsk tsk' would be more frequent if it was the pads, on mine it was basically once a rotation, and as the pads stay still and the rotor rotates, it made sense it was the rotor having a kink. You can true a rotor with the a spanner.
When I've had this problem the rotor was a bit bent, and squeezing the brake just lightly touched it to the rotor evenly through its rotation which stopped the 'tsk tsk'. I realised when it occurred to me that the 'tsk tsk' would be more frequent if it was the pads, on mine it was basically once a rotation, and as the pads stay still and the rotor rotates, it made sense it was the rotor having a kink. You can true a rotor with the a spanner.