- what is the cause of Axle Shaft damage

DETAILS! What kind of damage? Front or rear? Noticed during the brake repair or supposedly CAUSED by the brake repair. What advice was given? Who gave you that advice?

they are telling you that the boots probaly are ripped or came loose. this will cause dirt to get into it and eventualy ware out the cv joint this is easily noticed during a brake job. if your mech. told you it was something to think about instead of it needs to be replaced right away then keep him. they will start to click when turning when they ware out