If the option to delete all browsing data on exit is enabled, Brave will occasionally perform that action, even if the user does not close the app and only switches to another on Android, e.g., via the app viewer for a short period.
I’m using the latest stable version of Brave to date, available for Android via the official Brave repository.
This issue has occurred on GrapheneOS and LineageOS without Google Play Services or a replacement like MicroG installed.