My point of view is the problem is hard to fix because there isn't a single cause.
It appears that your Mac is asleep normally when something occurs that wakes it. Network activity, a timed maintence event, or a third-party program can fire the wake up signal. You Mac wakes as requested. Because the wake was not from the UI the Mac wakes in "dark wake / maintenance wake" mode. The display remains dark, keyboard, and mouse are not activated.
During the maintenance wake the Mac takes care of the condition that triggered the wake and then wants to go back to sleep. If you check the system log you should find a sleep command followed by a sleep failed command.
Programs can tell the system that they are not in a state to be put to sleep when the system wants to sleep. This is to protect critical operations. It also prevents your Mac from sleeping during a movie or when showing a Keynote presentation. Lots of other programs, both Apple and third-party, can tell the Mac not to sleep.
Something in the Mac tells the system not to go back to sleep following the maintenance wake. What that something is can be any app running at the time. On my machine its the XYZ app. On your Mac its the FGH app. On another user's machine its the ABC app. Or it might be a combination of apps.
The point is that during testing my Mac would wake in dark maintenance mode to handle the wake event normally. Once the event had been handled (all normal to this point), the Mac attempts to go back to sleep. This is where the sleep failure happens. The Mac never goes back to sleep.
When the user attempts to "wake" the Mac its not really alseep. It appeas to be asleep because the screen is dark. Nothing will wake the Mac because its already awake in the dark maintenance mode.
The bug really is finding out what is blocking the Mac from returning to sleep.
As always, this is my situation and others may be seeing other issues here. Bottom line. This is a complicated issue.