GFC Highlander Owner

While driving I get a warning and message that my Emergency Break is Engaged (which it is NOT). First visit to mechanic I was $600 later the problem still exists. First started in March. This is June and still happening. Does not happen on regular basis. I never know when it will come on. Alert is very annoying. Second visit to mechanic I was told they cannot find anything wrong. Cannot believe that in this big Toyota World, I am the only one with this problem.