In most of the recent device, apps are not allowed to work in background when the device is idle. This is to extend the battery life. Apps will only work when the device is active. And if the power saver app kills the running apps for running in background there will be no other way but to reinstall Remote Call Recorder.
Fortunately, there are ways with which you can either disable this power settings or add the required app as Whitelist to be allowed to run in background.
Below is the list of Device and their corresponding power setting screenshot. Please note that these are external links.
Some Android 8 Phones
OnePlus and Huwei Android 8 updates have bugs that puts apps to sleep even if they have on going notification. Try disabling battery saving mode for ACR if you experience such issue.
OPPO Android 8 and above
Samsung ultra data saving