There are two additional ways to resolve the problem, other than a 2-button reboot:
1. Unplug the Pro immediately (soon) after 100% charge is reached. Operation will be normal.
2. If you have another 12-watt Apple charging puck, use that. Operation will be entirely normal.
Make that 3... Call your Apple dealer and request a replacement charger. It will be cheerfully replaced.
iPad Pro Wi-Fi, iOS 9.1
What do you mean by "cheerfully replaced", free of charge ?
We had 2 Pro's with this problem; their power supplies were replaced free at our Apple Store.
Note: one of the 2 Pro's has re-developed the same problem, so it is possible that there are more complex issues or another bad power supply was received. We hope Apple is continuong to research this issue for a permanent solution. Since it is apparently not widespread, there may have been QC issues on some early-production units.
Solution to Black Screen startup on iPad Pro
