With mine i have been out three times with the loan Nikon 80-400 and had no problems,if i had just had it a few times and no one else had been troubled with it i may have ignored it but it does appear to be a problem with a lot of NIK/TAM combinations.
I just tested it inside and it seems to work fine. What I noticed is I locked the focus with that switch at the back. It's normally only the focus points it locks so I wouldn't know if that had something to do with it or if it is like the focus freeze and will just happen for some reason.