There are number of things you need to be aware of:
Your xpath is very brittle and not reliable - you need to refactor it and make it shorter using a relative path expression (//)
Any browser in headless mode gets executed in a different system profile then the logged in user. So the resolution is usually smaller and can affect the responsive display of the page or website. Take a screenshot of the test and you will see the full-screen is not the same as the full-screen when not in headless mode.
When you a have refactored your xpath you then need to make sure that the same window resolution is in both headless and headful mode. Any difference will cause the page to be rendered different and hide or change some elements.