Could be this defect? Even though your iPad was manufactured a month after this issue was resolved. https://support.apple.com/en-gb/ipad-air-3rd-gen-program-for-blank-screen-issue I went into an Apple Store and after much persistence the Genius replaced my iPad under this program. My iPad had power, but a blank screen, or brief flicker. Worth a try I think, good luck!
Great video, pics and guide. I will definitely not be opening up my iPad Air 3 to fix it. I shall leave it to the experts like you!