I'm creating a new thread specifically to document this one particular issue of the new S25 series running Android 15. The other thread about notifications was getting cluttered with discussion of a range of issues.
Discussion here should be only about this one problem: You unlock the phone and only then get notification alerts (could be visual and/or audible depending on the app settings) that are time stamped for right then, but which you know should have alerted you earlier before you unlocked the phone.
Please do not post here about other notification problems, such as issues displaying content of notifications vs icons, not receiving notification sounds, notifications not appearing but time stamped as delivered earlier, not receiving notifications at all from certain apps, etc.
Cause: The problem appears to be the result of changes in Android 15 which makes "doze mode" (which puts apps to sleep to save battery) more aggressive and/or less compatible with some apps. The Pixel phone users who have been running Android 15 for a while now have had this same problem, so it is not a problem specific to the S25. It seems unclear if this is a bug in Android 15, or if certain apps are not complying with Android 15 changes to allow the notifications to come through prior to unlock.
Solutions: For one particular app, I found going into the app info menu, then battery, setting the option from "optimized" to "unrestricted" seemed to fix the problem. I believe this setting is intended to allow all apps to bypass doze, but doing this did not work for a couple other apps having this problem. For the problem apps, I had to connect my phone to a computer and use an ADB tools command line "adb shell dumpsys deviceidle disable" - doing this completely solved the issue for remaining apps I had problems with, and also solved the problem for the first app without having to set it to "unrestricted."
Attempted fixes I've tried that did not work:
Doze Stopper app from the Playstore. Some people have reported this can solve the issue, but it did not work for me.
Settings, Battery, Background usage limits, and adding the apps to "never auto sleeping apps"
Settings, Battery, Background usage limits, turning off "put unused apps to sleep"
Settings, Battery, turning off power saving
Settings, Battery, turning off battery protection (or using "basic" mode vs "adaptive")
App info for the app in question, turning off "manage app if unused"
Connections, More connection settings, Private DNS (changing to automatic, back to off)
Factory reset, I replicated the issue with the same problem apps on a fresh out of the box S25 that had no setup done except installing only those few apps I had this problem with directly from the app store.
Unzip and put contents in a root directly, like c:\adb. Run a command prompt ("cmd" from windows menu), go to the adb directly you created (cd c:\adb). Plug your phone into your computer, and type "adb shell dumpsys deviceidle disable" at the c: prompt. Your phone needs to have developer options enabled, and then USB debugging enabled within that menu. You also have to allow the computer to access the phone with an on-screen prompt that will appear after you connect your phone.
