Flutter Developer Needed to Fix App Crashes (Auth, Data Loading, & Video Buffering)

I have an existing Flutter application that requires urgent bug fixing and optimization. The previous developer left the codebase with several critical performance and architectural issues that need to be resolved. Current Issues to Fix: Authentication Crashes: When multiple users attempt to sign up or log in simultaneously, the app crashes, and users are unable to complete the authentication process. Data Loading Failures: The app frequently fails to load data properly, resulting in blank states or broken UI components. Severe Video Buffering: The app includes course videos, but the video playback experience is broken—it buffers constantly (e.g., playing for 3 seconds, stopping to load, and repeating). What I Am Looking For: An experienced Flutter developer who can dive into an existing codebase, diagnose why the app is failing under concurrent user traffic, fix the state management/API calling issues causing data drops, and optimize the video streaming delivery/caching layer.