Why video recording scheduler is not working?
Nowadays devices are coming with more security in context of Battery power consumption. By default devices keep almost all apps in power saving mode. It means in some devices your background work (Location, Alarm manager) won't work as soon as you come out from the app. In other devices background tasks won't work after a battery threshold limit (like 13%). So you need to keep out your app from this battery saving mode to run your app smoothly even in background. The way to achieve that behaviour is,
Xiaomi
• Go to the Battery => Power => App battery Saver => select your app and choose No restrictions (for Background settings), then Allow option for Background location.
• To AutoStart your app after Boot: Go to the Security app => Permissions => Auto start and check your app.
Samsung
Samsung Smart Manager App used to stop all background work after 3 days if you don't come to your app. So the way to disable this feature is,
• Go to Battery in the Settings => Unmonitored apps => Add your app to the whitelist. Some other Samsung versions may differ the place to disable it, like Battery => Detail => Select the app and "Don't optimise".
Lenovo
• You need to go in setting => application => select app => uncheck Restrict to launch
Other phones
Try all the above options, it should work with those options.