When a user is in a field and wishes to verify the value, hits ENTER key. Instead of the current field would turn green and the cursor would move to the next unverified field, the cursor does not move, and a dialog appears which says "There are no unverified characters in the task."
The main rootcause of this behavior was the option "Go to Uncertain Field on Confirmation" enabled.
It can be enabled in the context menu if you right-click at Data Form of a document in Document Editor.
Uncheck "Go to Uncertain Field on Confirmation" option in context menu.