I have the above mobile device for just over a year now. Battery is normally very good.
My experience is that with 100% charged battery at night and wifi and mobile data off, the device lost about 4% overnight, say 8 hours.
In the last 2 weeks it has been losing 25-30% battery in standby.
During the day by battery drain is normal like it always was.
As a test I put it in Airplane mode and lost only 3% overnight.

I have searched the net for a possible solution and came up with nothing.
My only correlation is that a software update ran a few weeks ago. I cannot be sure that the battery drain on standby is directly linked to the software update.

Would appreciate any advise from the tech savvy members.