I am running Lightroom 6, the stand-alone version, on my 2013 Mac Pro with 64 GB of memory and OS X 10.9.5. When I lock my screen using Keychain and leave the computer for a while and come back, Lightroom 6.0.1 is Not Responding. I have no choice but the Force Quit. LR5 did not do this, but LR6 does. It is most annoying.