Battery Optimizers - OnePlus devices

Background

Battery managers allow mobile devices to extend their batteries but many times at the expense of performance, notifications and even shutting down background services. When in Child Mode, Boomerang needs to run as a background service and on some devices with an aggressive approach to battery savings, can break our background service.

OnePlus devices use a modified version of Android which they call Oxygen. The OnePlus 5 and OnePlus 6 devices seem to have the most aggressive battery optimizer that could affect Boomerang's background services when used on a child's device. 

Try the following steps if you are finding Boomerang is not blocking apps or reporting app usage data on your child's device.

Solutions

1. Turn off System Settings > Apps > Gear Icon > Special Access > Battery Optimization.

WARNING: Recently OnePlus phones started reverting this setting randomly for random apps. So if you set it to be not optimized, the next day it may be back to optimized. There is no workaround and you may have to check system settings every once in a while.
See a bug report filed to OnePlus. 
To avoid the system to automatically revert the not optimized setting, you must also lock the app into the ‘Recent App’ list. (solution described here) 
Start the app you want to ‘Protect’. Press the phone Recent app button. Toggle the Lock button on the upper right corner of the app. This will avoid the app to be killed in background and the Battery optimisation setting to be reverted.

2. On some OnePlus phones there is also a thing called App Auto-Launch which essentially prevents apps from working in the background. Please disable it for Boomerang Parental Control.

3. Also try: Phone settings > Battery > Battery optimization and switch to the All apps list (Top menu) > Your app > Don’t optimize

NOTE: You may also need to disable Doze mode in Developer options in 1+3 and earlier. Also disable Settings > Battery > Battery optimization > (three dots) > Enhanced optimization. This option may also be called Advanced optimisation.

Tips from https://dontkillmyapp.com/oneplus