I've been paying some attention, and I've found that I'm seeing two different things.
Some of my delays occur when I hit "Change Post" to complete an edit, and they register in the "Generated...." notation. (
Example 1...
Example 2)
But I'm also seeing delays which don't register as taking an unusual amount of time of to generate.
This now rings a bell! A similar, if not the exact same, situation cropped up some years ago, and as I recall, it ended as mysteriously as it began.
One more...even longer! 
