We are having an issue with our '98 Outback's brakes. It seems that they will randomly decide not to work. It is winter here, but the problem occurs after the car has been warmed up and driven. Usually occurs during slower driving. It feels as though when the brake is applied it wants to kick back making it hard to apply any pressure. We've already run a couple of stop signs. Next thing you know its gone, no problem. Happens about once a week. Any thoughts?