Report org headings with duplicate names in the *Messages* buffer. Reveal them and move to the last duplicate. Run after saving the buffer.

org-duplicate-heading.el

  (require 'dash)
  (defun org-duplicate-heading ()
    "Move to duplicate heading in the current org buffer."
    (interactive)
    (let ((header-list '()))
      (org-element-map (org-element-parse-buffer) 'headline
        (lambda (x)
          (let ((header (org-element-property :raw-value x))
                (begin (org-element-property :begin x)))
            (when (-contains? header-list header)
              (message "Duplicate header: %s" header)
              (goto-char begin)
              (org-reveal)
            (push header header-list))))))

    (add-hook 'org-mode-hook
              (lambda ()
                (add-hook 'after-save-hook #'org-duplicate-heading)))