Which site is this occurring at? We can see some related issues when you post a url to your site. Without, and based on the info. you have provided, we will be hard pressed to respond.
Deactivate all plugins. Test site. If still same issue, then it is most likely the theme. If issue goes away, activate plugins one at a time, test site after each activation. If issue returns then the problematic plugin is the last one activated. If not a plugin issue, switch to default unedited theme. Test site. If same issue, then perform a manual update to WP. At that point you are running a default WP install, consult host.