Ipad Mini 4 battery drain

Been having an issue on both new iphone 11 and an older Ipad Mini 4 where battery drains. It seems that biggest culprit is ""Recently Deleted Apps" but apps were deleted several days ago so this should not be still the case for the last 24 hours monitored in the battery setup menu. Previously it seemed to be the iphone mail app that was draining so I deleted this app completely. However I continued to have thew battery drained overnight when not charging and dead by the morning with Recently deleted apps as main usage.

I did a factory restore on the Ipad4 and restored from the icloud backup. The iphone 11 was new last week so set up from my older phone.

Most recently the iphone is better in as much as the use of battery is slower but even today so far it shows recently deleted apps as using 100% of the battery decline although this use is very low (battery still showing 98% in about 3 hours).

However the Ipad battery was empty by morning and shows a steady straight line rate of battery use during the night. I used the ipad last thing for an hour 11pm-12 while not being charged and the period between 11pm and 12 midnight shows use as safari 78% Home and Lock screen 8% and other normal apps Amazon, Settings @ 5% each. After 12 midnight every one hour period has the same rate of decline in battery but "usage by app is not available" until the unit was dead by 8am.

Any ideas and help appreciated, I have exchanged instant message with Apple support but their advice was to swap the iphone 11 for a new one, I am sure it is not a hardware issue on the iphone.