Try clearing the wallpaper app data 1. Open Settings. 2. Select Apps 3. Tap the "three lines icon" and enable show system apps 4. Locate wallpapers & Styles or any variation that points toward the built-in service that deals with wallpapers. (Should be two wallpaper apps) 5. Open it and select Storage. 6. Clear data and restart your device
Also, A third-party wallpaper app (that you may have downloaded) may be causing this behavior. Inspect the app settings and look for the feature (setting) that automatically change wallpaper daily.
I'm having the same problem. It seems to be the Dynamic stock wallpaper and it reverts back to the 'S' between 7 and 8am Eastern time US. I've tried every suggestion I found. Finally I texted them through the Members app. They did troubleshooting for quite a while. Basically said to try a non Dynamic wallpaper. They had me submit a report with logs. They said the more it's reported hopefully the quicker it'll be fixed. I encourage everyone with this problem to submit a report via the Members app.
