This error typically occurs when Git is unable to lock a reference while performing an operation. It can happen due to various reasons, such as file permissions, conflicts with another process, or corrupted repository state. 

Here's how you can troubleshoot and resolve this issue:

Check for Running Processes: First, ensure that there are no other Git processes running that might be holding locks on the repository. You can check for any running Git processes using the Task Manager (Windows) or the ps command (Unix-like systems).

Delete Stale Lock File: If you're sure there are no active Git processes using the lock file, you can safely delete the lock file manually. 

rm '/Users/<example>/repos/<test_repo>/.git/refs/remotes/origin/main.lock'

Retry the Operation: After deleting the lock file, try rerunning the Git operation that caused the error. If the lock file was indeed stale and causing the issue, the operation should now succeed without encountering the locking error.

Check File System Permissions: Ensure that you have the necessary permissions to modify the lock file and the repository files. If you encounter permission issues, you might need to adjust file permissions accordingly.

Verify Repository Integrity: If the problem persists, it's possible that the repository might be corrupted. You can try running git fsck to check for any integrity issues with the repository and attempt to repair them if necessary.
git fsck

Clone the Repository: If none of the above steps resolve the issue, consider cloning the repository again from a remote source. This can help ensure that you have a clean copy of the repository without any locking issues.