When brackets are matched and the edit area loses the focus, e.g. by moving the vertical scrollbar, the highlighting of the brackets - in difference to all other highlighting - disappears. This is a problem when the matching brackets are far apart.
The problem might be that erasing the highlighting is a function of the event "losing focus", because without focus the caret (inserting position) is undefined. Maybe, the problem will be solved when erasing the highlighting is like setting a new one a function of setting the caret.