Theres a slideing clip on the arm that holds it onto the splined drive nut,its either broke/missing or not seated all the way down. The spring in the arm could also be broke, causen it to not keep tension on the windshield.
I don't have a picture but am going through something similar. The passenger side wiper when laid completely flat cannot exceed 20 inch its mor like 19 1/2 long. Here is the problem...the stock wiper arm connects through the lowest point in the stock wiper. Its a male on the arm and it goes into a round hole in the wiper. The new wipers are universal the attach at a higher point which causes the arm to sit to high and hit the hood. You need to look around for the right wiper. I changed my passenger side with the universall type and it also is touching hood. I haven't been able to find the right wiper yet.
Also check one more thing. Make sure where the arm attaches to the gear is seated right. Compare it to the hight on the good side. If the arm has slipped up on the gear it will also cause this problem but you will find this in the messurement of both. If this is the case there is a clip at the base which grabs the gear it has to be compressed with a screw driver to remove the arm or to push it down lower.