In a new Firebase project, the very first file upload to Firebase Storage succeeds as expected. However, all subsequent upload attempts to Storage fail. The process hangs for a long time (several minutes) before failing with a permission-denied error, even for very small files (e.g., 87KB).

Crucial Detail: The same function that handles uploads works perfectly every time if no file is selected (i.e., when it only writes text data to Firestore). The issue is isolated exclusively to write operations on Firebase Storage.

Troubleshooting Steps Already Taken:

Verified and tested multiple Firebase Storage and Firestore security rules, including rules that allow public writes (allow write: if true;).

Confirmed all relevant APIs (e.g., Identity Toolkit API, Cloud Storage API) are enabled in the Google Cloud project.

The upload failure persists even with a small (87KB) test file after the initial success.

The issue persists even after creating a brand new Firebase project and setting it up from scratch.

The test was performed in a clean browser environment (e.g., a fresh install of Microsoft Edge) after clearing all cache and cookies, ruling out local extension/cache issues.