Wow. This isn't a reply, but a cry for help as well. My B is a little over 1.5 years old, and about 4 months ago started the EXACT SAME behavior! It started with him jumping up on people with the small nip (easiest to deter). Then when someone bends down to pet him, and he approaches + accepts on his terms, as they pull away/stand/bend up, he quickly and out of nowhere will bite the very hand that was just getting him! It hasn't been hard enough to draw blood, but definitely leave a mark. Then the most recent is out of nowhere, without warning like the others, if someone walks within reach while on the leash, he will lunge and try to bite them. A man was walking the opposite way on the left side of the sidewalk, I was on the right side, and Massimo was on my right, sniffing/walking in the grass. As the guy passed us and without any indication, he darted over and grabbed the guys leg. Then last week he actually got one of the maintenance guys in my building who he has met/interacted with on multiple occasions while he just walked passed us while at the mailboxes. The majority of the individuals this has happened to have been male, but women aren't excluded either. Otherwise, he is normally very sweet, affectionate, loves to play, super friendly, and loves meeting new people and, for the most part, other dogs. Although this behavior is embarrassing, what really concerns me though is that for obvious reasons it leaves a bad taste in people's mouths, and people love to talk, in turn causing people and their dogs to avoid Massi which breaks my heart. Please help!