Question re: filters

The lens has been checked by Nikon and they didn't find anything   wrong.

You can try yourself how easy is to remove lama's saliva (whatever it is). Go to the ZOO and ask nicely that cute animal to spit on your $2400 lens.

I don't know if you have a dog, but if you do,  seems not to be as talented as mine, at least doesn't like your lens as my  little beast  like mine.