The way the wiper system works is the motor always powered by a hot wire and the wiper switch removes the motor's ground when it is off. There is an internal partial ground in the motor that removes the ground when the wipers approach the parking position. So your motor's partial ground is broken or the wiper switch is not removing the ground when the switch is off that could be your problem. There is another possibility and that is the intermittent control for the wipers is broken. Again this control supplies a intermittent ground to the wiper motor. If is supplies a continuous ground to the motor the wiper will continue to work. Usually this is caused by a stuck intermittent wiper motor relay.
Jim & Roy Davis
2016 Hurricane 31S
1961 Rampside in tow
I had this problem on our Southwind. The cause was that the wiring harness plug behind the hood was getting wet. It took a while to figure it out, but once I pulled it apart, blew it out, then wrapped the whole plug with electrical tape, it never happened again. Don't know if this is your issue, but it might be worth checking it out.
Vicki and Mike, Aria 3901- The Wined Up Bus