I'm new here and haven't read all 70pages, but can't believe that people say "it is working as designed"
I have the same problem on the 6plus with newest ios. did some testing and figured, that after 30 min or so when switching back to an app it is refreshing from start. It does refresh also maps app (deletes the address I have entered) photo app, music app and starts from scratch
It drives me crazy as well.
very basic scenario: I close all apps. So no RAM issue. Start maps app. enter an address for route planning. press the home button. wait 30 minutes. open app switcher (in the app switcher I see exactly where I left the app including my desired address) switch back to maps, it opens, shows me the app where I left it, BUT after one or two seconds it refreshes and starts the app from scratch. My address is gone! What exactly is here the reason for this behavior design?
The same with photos. I enter an album, scroll endlessly to some specific photos I want to show somebody, press the home button, (because I may need to do some other things until i want to return to the specific photos) and after 30 minutes or so I return to the photo app (again: in the app switcher the exact state is saved) but after switching back, the photo app reloads and shows the overview of the different albums.
Very annoying and it happens with almost all apps, excluding the calculator!!! - hey, this app saves the state you left, even after killing it - so it can be done, apple! You promised it: "When you switch back, you can pick up right where you left off"
And for all refresh lovers here: a simple refresh button or an auto refresh as an option would do it for you!