Hi Steve,
Going back to the post I've made previously
here, method 2 is what you need to use. It will work as long as the park signal is greater than 20mS long.
It doesn't matter how far past the park signal you go then, it will stop no matter what. In fact you could deliberately park the wiper at a time after the park switch if the switch was in the wrong position. You would have to move the set-reset operator into a condition instead of the motor output, and use the result of that condition to drive the output with a time delay when turning off, Set-Reset condition = true, false for 0.2s for example.
If you need more detail, please let me know.
Cheers,