React Web App Bug Fix

I maintain a JavaScript/Node.js web application built with React and one feature has started misbehaving. I will provide the repository link, clear steps to reproduce, the current versus expected behaviour, and any relevant environment details. Your task is to reproduce the issue, isolate its root cause, deliver a concise fix that touches only the code involved, and verify the result with a test or other reproducible check.

To keep things tidy I need:
• the corrected code committed to the existing branch
• a test or manual verification script that proves the fix works
• a brief summary (one-paragraph release note or commit message) outlining what changed and why

Please let me know how quickly you can turn this around when you respond.