I like Ry the Car guy, the Xterra / Frontier / Pathfinder are similar at the front.
@4:56 of the video, you can see the driver's arm connects.
It looks like there is screw (s) that connect the right and left arms and you don't have slippage at the wiper spline.
By lifting the cowl you can see which end has the play (at the motor or at the wiper).
Hopefully it's just loose.
I haven't done this myself, but it looks about 15-20 minutes to get in there and inspect it.