When playing a slideshow within Lr CC the show sticks to the playback screen and cannot be removed. If the show plays on the monitor containing Lr the show will cover the Lr interface and gets stuck on the ending slide and cannot return to Lr. Escape or windows minimize cannot remove the show.
If I play full screen on my second monitor the show plays and I can stop it by escaping but the screen still shows the last played slide. It cannot be cleared. If I play the show over the Lr main interface I cannot get visually back to the Lr interface. I need to Ctrl+Q to exit Lr.
Running multiple monitors with Windows 7 and Lr CC. GPU acceleration is not enabled.
I have reported the issue here: Lightroom CC slide show gets stuck