I frequently am having complete system freezes when I resume from sleep. It seems to only happen if I am connected to my external display (Dell P2715Q). The symptom is that the screen is complete frozen on my MacBook Pro, no signal goes to the external display, and the system is completely locked up to where I cannot even press the trackpad. To recover I have to power off completely and then I get the "your computer restarted due to a problem" message. Anyone else facing this issue?