Apple won't believe me

I got a IPod touch 6th gen 64gb and a couple of months I noticed some pixel damage around the edges while trying to watch tv on my device. I took it to my local certified Apple repair place and got it replaced under its warranty. Not 12 hours after receiving the new device I noticed the exact same pixel damage in the exact same spots. I reported this to to apple and the repair place. The repair place "claims" that the technician couldn't find anything wrong with it yet the girl who served me at the counter could see it. When I spoke to a apple case worker on the phone they said it was the backlight that I was seeing. That would make sense if it was a straight line of lighter pixels around all the edges or along the bottom of the device instead of being patchy and uneven along two sides. Has anyone else had this problem?