Top photo is of vsld shafts, they are unequal length as shown in the pic.
The open diff uses the equal length shafts shown in the bottom pic.
If someone swapped in an open diff the spot where that circlip seats is not in the correct position and the shaft might walk a bit.
Google images for the win
I just knew what i was looking for.
If all is correct I can't help but wonder if the issue could be related to a bad cv shaft or even a bad diff bushing. When you pulled it out before was there any slop in the cv joints? That rear diff bushing is a common issue as these cars age. Unfortunately Nissan doesn't sell the bushing independent of the rear subframe so you'll have to go aftermarket unless you want to buy the $800 rear subframe. Pressing the old bushing out is a real PITA if you leave the subframe int he car but doable.