Improper Shutdown Problem
I have two computers giving the same problem. Suspect OS 10.11.x or Adobe. Have not checked Crash Log yet.
Both computers will only partially shut down automatically as determined by the shutdown requirement procedures meaning a black screen and an arrow or just a black screen.
On one I removed all startup items and shut off all app to allow it to shut down w/o open apps interference including any screen saver. The problem continues.
On the other I removed screen save requirements and reset the SMC and problem continues.
Problem did not come about until both computers were upgraded to OS 10.11.x. At about this same time the Adobe Download Manage seemed to showed up meaning it a dialog box on the front screen at startup. Was able to remove the icon on the Finder menu bar.
The problem does not make sense to so this description may not explain the problem accurately. All I can says both computers will not fully shut down either by timed shutdown requirements nor by selecting shutdown in the Finder dropdown menu.
MacBook Pro with Retina display, OS X Yosemite (10.10.5), Other Mac's linked to Airport