Is this a crazy theory on part of the problem? When looking at mine (see pics below) mine doesn't look close enough to the corner of the plastic for that to have caused the problem on mine, mine looks like the very tip/corner of that piece of bodywork has not been sprayed enough...
...my theory on the others you guys have posted - is it related at all to closing your bonnet/boot???!!!
I watched this particular spot as my wife slammed the boot shut and you get a LOT of movement when doing this - I've not yet opened/closed by front bonnet but now wondering whether it's that nasty drop you do on the bonnet that could be what makes the close contact between plastic + bumper hit each other more???
Worth watching as you drop your lids, go on, go outside and try it a few times...
