The System Administrator attempts to edit a record that is loaded through a VisualForce page, such as a Call or Survey, but no action occurs.
This error occurs when a System Administrator has the option Development Mode enabled on the user record.
This is a Salesforce feature used by Developers to assist in the creation of VisualForce pages.
Users should not be using Development Mode as it can block some types of requests sent by VisualForce pages.
Disable Development Mode on the User record.
Salesforce Documentation: Salesforce Development Mode