If the wires were shorted in The harness how would unplugging the washer pump fix it? You have a back feeding problem. Either a bad MFS or power back feeding through other circuits looking for a ground.
I have seen wipers come on with blinkers 2 times before and both were bad grounds. Your case could be something different, but I would eliminate the ground as a culprit first since it is very easy to do.
Remove the ground wire from the stud, jump it to a known good ground. The battery is ideal. If that doesn’t fix it then we can move on to the next likely item.