One problem related to automatic transmission park/neutral start switch has been reported for the 1997 Mercury Sable. The most recently reported issues are listed below.
Vehicle exhibits an intermittent neutral condition after driving and coming to a stop (I found service bulletin number 983112 on nstha web site) almost caused an accident when brake was released vehicle rolled onto busy highway and I had to come to a complete stop almost struck by semi. Mercury dealer did not find a problem. I can never tell when this is going to happen. There is absolutely no warning.