I’m afraid I can’t reproduce this issue on my end. Could you please tell me which version of ACF are you using?
Also, are you using a cache plugin on your site? If you are, could you please clear the cache and test it again?
It’s also possible that there’s a conflict on your site. 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. You can also check the console on the developer tools of your browser to see any error messages on the page.
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