The lockups are common with any iPad. I did have a unique one yesterday with my new 12.9 though. I had it with me at work, and the screen went to sleep while I was talking with my boss. When I came back I couldn't get the screen to wake up, just nothing but black. I did feel like I could see a very very faint image of my app window, but not enough to really see anything. After hitting the home button maybe 10-20 times finally the screen work up and I could touch my finger tip to get back in. Anyone ever experience anything like this? (No not on iOS 11)