Hey @ccarter3,
Thank you for providing the credentials. I checked your setup and the issue was happening due to your custom CSS added in the Appearance > Customize > Additional CSS. I commented the code related to sticky topbar and this has fixed the jumping issues.
Please note X header was not designed for in-depth changes as we often receive header related customization questions or requests and this was the reason why a header builder was created in Pro . If you need in-depth changes, please consider upgrading to Pro so you can build a custom header yourself without custom coding and this will also cater your mobile sticky header issue.
To setup sticky headers in Pro, see https://www.youtube.com/watch?v=jEZ8B7E1wgE
Hope this helps!