Can you check in the App Permissions area to see if there are any settings that allow you to turn on an Always Allow function?
I am confident that the setting exists on Samsung Galaxy s8, I just don’t know where exactly it is. We have other users that have the same device and the setting exists. With the release of Android 9 and 10 there are built-in low-power integrations that can cause that issue when it goes to sleep many functions are halted or put on reduced performance to conserve battery life. This includes GPS function since it isn’t an essential service to be running while the screen is turned off.