Comment 129 for bug 1566302

Did you nuke xscreensaver and or light lock. If you disabled all else (for testing) the last option should apply prior to resuming.

Blinking Green power = Suspend
No light on power = Hibernate
Solid green power = xautolock, screensaver, or equivalent

Prior - I could make hibernate and suspend work consistently (inside 10 minutes). If the last option is causing the issue the screen will go black at exactly 10 minutes. The only way I could resume properly every time was to remove them.