macOS Sierra won't wake up from display sleep

Since Sierra was released right up until today, on my MBP Retina (late 2013) I experienced this issue and others such as:

• Unexpected shutdown / restarts
• Failure to shut down (black screen indefinitely)
• Full system freeze, including mouse/trackpad pointer
• Constant general slowness, frequently grinding to a halt

I am a web developer, so I don't ask as much of the system as would, say, a video or music producer.

I had tried the following on multiple occasions:

• Adjusting Energy Saver settings
• Starting up in Safe Boot mode
• Disk Utility via recovery partition
• Resetting SMC
• Resetting NVRAM
• Reinstalling Sierra (short, temporary relief)

None of those helped (except for reinstall, but only short, temp).

Error logs and Activity Monitor didn't reveal much,

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On a whim today I tried disabling Apple (iTunes) and third-party background services:

• DropBox
• Transmit menu
• iStat menus
• iTunes Helper

It appears to have resolved the problem with dramatic success.

I don't know which one was the primary culprit. Probably DropBox, followed by iStat, or maybe DropBox in combo with Transmit which both have OS / disk-related dependencies.

I've added shortcuts to these services to my Dock so I can activate them manually as-needed.

I found this on Redit and it worked for me. My display wasn't going to sleep at all.

I went to printers and scanners, and control clicked on the left side of the window where devices are listed, and reset. seems to have done the trick as of right now.