I think more than 2/3 of B14 Sentras I come across have had their bumper whacked and then get the funny misaligned damage gap right behind the tires even though many of the bumpers don't look very damaged.
My Sentra has that problem too. Wish I could fix it easily.
Our bumpers must be fragile as all hell. I read that they are easy to take off and there are lots of clips--no wonder.
^ That is exactly what I see all the time. However, my little Sentra got some rear bumper corner bruises on the drivers side from the previous owner so I assumed the sagging was from getting hit.
From some earlier searching--it looks like it can be fixed with getting new bumper clips. Have your or anyone tried?
My bumper clips are all fine. We got some new ones from the lot we bought my car from because they assumed it was the clips as well, but when we went to put the next clips in (after taking the old ones out) they didn't change how the bumper lined up.