Favorites are currently stored with the app data on your device, so you will remove them if you clear your app data or if you reinstall the app. Our app needs the Storage permission to save favorites, so you may want to verify it's activated. We recommend checking this page to know more about app permissions.
We received some incidents about favorites randomly disappearing from Favorites section, and we're currently working on a long-term solution to improve the way favorites are managed.
Got questions? Contact us at firstname.lastname@example.org!