Hi @wax
Could you please share the code you have so I can test it out on my end?
I also tested it using the example on the documentation but failed to reproduce the issue. Could you please try to reproduce the issue on one of the WordPress’ stock themes (like Twenty Sixteen) with other plugins deactivated? If it disappears, then you can activate the theme and plugins one by one to see which one causes the issue.
Thanks 🙂