The problem is the point set under the plastic cover on wiper motor. The points trigger as the motor rotates. This tells the location of the wiper arms to a small circuit board under the points which controls the delay and wiper speeds. When these points fail the wipers will no longer go to the park position because there is no signal. The proper fix is to replace the motor, but if your mechanical you can pull the cover off the motor and try to repair it. On mine the point arm fell out. I made a new one from some steel banding and glued it in with a small amount of 2 part epoxy(be sure to sand the paint off the steel banding) I.m not sure how long it will last, but mine is going on a year now. Its simple enough to get at if you want to give it a try. outherwise a new motor is around $70.00.