Node.js Backend Bug Fixes Needed

My web app runs on a Node.js backend, and a recent regression has left several key features broken—specifically the movement logic and the real-time data synchronisation that keep multiple clients in step. The system isn’t suffering from performance or security issues; the problem is strictly functional.

What I need is a sharp pair of eyes on the current codebase (Express, Socket.io are in play) to pinpoint why these endpoints and sync routines fail, then patch them cleanly without introducing new bugs. Automated or unit tests that prove the fix would be a big plus.

Deliverables
• Working, committed code that restores movement and sync behaviour
• Brief summary of the root cause and the steps you took to solve it
• Proof the fix works—screenshots, screencast or passing test suite

If you’ve wrestled with real-time Node.js systems before, you should feel right at home here. Let’s get my backend healthy again.