I have DND set up to turn on while im sleeping, by a schedule starting at 6am to 2pm during weekdays, however, it turns itself on at 10pm every day for no reason. There is no schedule set up to tutn it on at 10pm, so i dont understand whats happening.
@Trun Have you tried wiping the cache partition on your device?
I believe there is an app that has permission to access the DND settings. Have you tested the phone in Safe Mode? This would disable all 3rd party apps that could be interfering. If this is the case, you would need to determine which app has the permissions and disable it or uninstall the app.