Hi there,
I see the problem on your site, but that seems unique to your environment. Most likely this is a conflict with another plugin.
Please try disabling ALL other plugins. If the problem is then resolved, re-enable each plugin one at a time until you encounter the problem again. Let us know which plugin is causing the conflict and we’ll try to reproduce the problem on our end and find a workaround.
If after you disable ALL other plugins the problem is STILL there, change to the twentyfifteen theme and test. If the problem goes away at that point, we know it’s a problem with your theme. Email us your theme with a link via our contact form and we’ll see what we can discover about that. https://wordimpress.com/contact-us.