I generally don't touch tablets, but i have done a couple of galaxy note tablets from 2015 one was a black screen and the other was lines on the screen. The issue was that the ribbon cable that goes over the battery from the LCD to the motherboard gets dislodged. A simple reseating fixed similar issues on that. I've looked at the construction of the Tab A and it looks very similar in design. It could well be that. To ensure no software bugs a hard reset is a good idea to test. If that's not helpful, i'd get it warranty repaired/returned...