Replacing faulty products with faulty products!

I bought a GoPro Hero 3 White and it worked till the camera started producing purple lines on the footage. I sent the camera back and with in a few weeks GoPro had replaced the camera with a new one and a new one year warranty. That camera worked for 6 months then produced the same purple lines. I sent back the second camera (in old housing) and they replaced it with a third camera with the new housing and a new warranty. With in three weeks the third camera produced the purple lines.... I sent the third camera back with two questions, 1) the new housing does not fit the floating back door, could they send back the old housing or replace the floating back door with one that will fit? 2.) Is there a possibility of me getting a different model Gopro so that I can stop getting the same model camera that keeps producing the same purple lines. Gopros reply: We will not replace the back door and so you would have to buy a new back door (R 399) and upgrading the gopro to a different model would cost an extra R2000. I now have the FOURTH gopro white and an unusable floaty back door! I have another gopro that works fine but continue to have problems with the white edition.