So I recently had my front bumper replaced and noticed a similar gap a couple months after the fact. Sure enough the brackets you showed were broken, I replaced them thinking this would fix my issue but it only made it slightly better and one side already seems to be popped out again. I had the bumper off when I did this and did not see the 4 points you placed your mending plates, are you referring to the part that protrudes out where the grilled clips in?