I found something strange yesterday.
Both Cortana and Windows Default Lock Screen were set to NOT run in the background, on the "Background apps" settings screen.
However, if I went to battery usage, and set it for the last 6 hours, when I never used it, first thing today, those two accounted for about 75% of the processing, under the battery usage, *if* I set it to the 6 hour interval.
Huh? Didn't make much sense, until I clicked on them, from THAT interface (some new items, such as System Managed, not just on/off), and noticed both were set to "System Managed".
So, apparently there's now a 2nd interface that manages background processing, not just the background settings, screen. If you see a high-drain app, go to the actual drain screen and look at your top offenders, I bet they're set to "System Managed".
I don't have any data to back this up yet, in fact I'm just recharging my phone this AM, so we'll see over the next couple of days, if this fixes it.
Hawwie_4, if you and others are seeing the same, try the above. I can post some screenshots if it'd help?
Edit: Settings (just the larger umbrella) was using almost all the rest of it, in the "foreground" even though the machine was asleep. I double-checked, and same deal, it was set to "no background" in the regular Background screen, but from the Battery Usage screen you can see it's set to "System Managed".
What a mess, I couldn't figure out how to set the tri-state battery settings, unless an app was already in the "draining" list. It sure looks like an oversight, that it should show this "System Managed" setting in the regular Background Apps Settings screen.