My trailer brakes are sometimes locking up when I am trying to back up, especiallly if I am backing up a hill. Doesn't do it all the time and I would appreciate some help if anybody has suggestions. I have the correct five prong plug. I have owned it for about four years and never had a problem till lately. I also have what looks to be oil getting on my right trailer tire. Don't know where that is coming from either. If anybody has any suggestions let me know.