Contact person: Flutter/Android App Intermittent Authentication Issue release Mode

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Location: Las Palmas de Gran Canaria, Spain

Budget: Recommended by industry experts

Time to start: As soon as possible

Project description:
"We are experiencing intermittent authentication issues in our Flutter/Android app, both with Google Sign-In and with email/password using Firebase Auth.
The most frequent error is ApiException: 12500 during Google Sign-In, and there are also failures when registering or signing in with email and password.
These problems occur inconsistently: some users can authenticate without issues, while others cannot, regardless of whether they are using the production or debug version.

The app is properly configured with the required SHA-1/SHA-256 fingerprints for both debug and release, the OAuth client IDs in Firebase and Google Cloud Console, and the updated [login to view URL] file.
The package name is correct, and the app is signed with the release key.
We have complete logs of the authentication process, login attempts, generated tokens, and Firestore configuration.

This issue affects both organic users and those coming from Google Ads campaigns.
We are looking for someone with experience in Firebase/Google authentication to review the details and help us identify the root cause and solution." (client-provided description)