We have 2 phones both with the latest System software, No WiFi and Location setting on, display shuts down with a magnetic case.
Both have the same App's my wife phone has 4 added app's, mine has the same app's plus more.
My wife's phone was draining the battery very fast 50% at idle in 12 hours.
Checking the battery drain was showing System use of 50% and Keep awake of over 12 hours, Plus NO Included Packages Showing.
My phone was OK.
So ended up removing the 4 added App's, Forced Stop on all app's that I did think that where being used, turned off the Location setting and re powered the phone, after some 10 min's the phone was back to normal System use of 4% and now showing Included Packages.
Its still OK after 2 days, so what was going on, have since added the 4 app's and still OK.
The 4 Added app's are 1Weather, ES File Explorer, Alert Me and Tunein Radio all added from Google.