Optimize AWS EC2 and GitLab

Our core application runs on an Ubuntu EC2 instance, and our deployment process involves pulling the latest code directly from the repository. Recently, we've been encountering server errors and failed deployments, specifically when executing a git pull on the EC2 instance, leading to downtime and development friction.

The immediate goal is to diagnose the root cause of these server and connectivity issues, restore reliable code deployments, and harden the server's configuration to prevent recurrence.

Here is what I need from you:

A swift, command-line diagnostic of the Ubuntu EC2 instance to pinpoint why git pull is failing (e.g., network, disk, permissions, authentication, or resource exhaustion).

Concrete steps to resolve the immediate failure and get the server operational and up-to-date with the latest code.