Device unique identifier not working as expected

I am using SystemInfo.deviceUniqueIdentifier to identify a user and look them up in a database to return their game data, however it seems that SystemInfo.deviceUniqueIdentifier will actually change. It seems to change when uninstalling/reinstalling the app and when OS updates are done. This is really problematic for me as it involves relinking an account each time this happens.

Does anyone have any insight into why this variable will change and maybe even a better way of identifying a...

Device unique identifier not working as expected