Warped discs

Having issues with warped rear discs. At 80000k I started to notice vibration from the rear when braking. Since the brakes needed servicing anyway I took it to the dealer for a brake pad change but what came out was that the rear discs were warped. They didn't know the cause of the issue but agreed to cover the work part of the cost so I only paid for the discs. Now, 10k later I feel similar vibration again when braking, seems to be the discs again... Has anybody had similar issues? My first guess is that the electronic handbrake have a role in causing this?