Bizarre. Looking back at the circuit diagram, I see only two ways that wiper motor can energize: (1) signal voltage to the purple/grey wire (“J” in diagram), which turns on the relay normally, (2) the black ground going into the relay (connector C2937S4) crossed with power and became a voltage source.
There could also be a problem in the park circuit, but I don’t think that could energize the wiper motor. The park circuit only delays de-energizing the circuit until the wiper is in the right position. In other words, even if the park circuit was faulty, you would still need to see voltage at that purple/grey wire or the black ground wire going into the relay, right?
If it were me, I would probably do the following: (1) plug the relay back in - make sure the motor is still engergizing, (2) once the wiper motor is moving again, remove the relay carefully (or maybe you can back-probe the connector?) and separately probe the grey/purple and black ground coming into the connector to see if there is voltage, (3) get a probe to stay securely in that purple/grey cavity, and then move the harness around in the back - see if any voltage lights up - same with black ground cavity. (2) keep that probe in the purple/grey cavity and see if there’s voltage while moving the CJB around in the passenger area (maybe use the max/min function on the voltmeter, or just have a helper monitor the voltage).
Any other thoughts here welcome.