Black or displaced screen when screen sharing headless mac mini on macOS 10.12
These are solutions that I found but that do not work for me:


UPDATE: The issue finally and miraculously disappeared after  updating to macOS 10.12.4.
If you run third party applications, such as AirParrot or f.lux, you should try completely uninstalling those, as discussed here. 
If your mac is 100% headless (i.e. no screen attached), you can either add an HDMI dongle or hack your own Thunderbolt dongle using a VGA adapter. This is a common trick to activate the GPU and comes with the added benefit that Screen Sharing gets much faster. This actually works for me, but is not a permanent solution to my problem.