Be sure the handle in the back is positioned as shown in the photograph below and pointing away from the inner motor coil. If you have it 180 degrees the other way, it may stop in the up position on the windshield. The handle can mount either way.
I had a problem similar to this. Changed wiper switch, wiper motor to no avail. The problem turned out to be the thickness of the washer under the wiper handle as this influences the wiper park switch contacts in the wiper motor also make sure that you do not have the nut mounting the handle on the motor spindle too tight. The original Ford workshop manual vaguely mentions this. Hope that this helps.
OMG my memory is gone. I just did two of them in 2019. I seem to recall a cam inside that breaks the contact at a certain poing. I took completely apart washed all the old dried up grease out and put the Lucas Red-N-Taky #2 grease in. Have not had that issue. There is also two positions for the wiper arms on the casting. Rotates a few degrees up in what I think Ford call winter position. I did not know that until another member told me.
When you turn the switch off the gear box rotates until it gets to the right point and stops. Something is out of time or not working right.