We have a 12 week old flatcoat puppy, he's our 7th. All the others have been pretty straightforward. But this one will not leave our older flatcoat alone. Constant ear biting, tail biting, and unfortunately our older boy is not reacting to the aggression. we have tried all the diversion tactics, but to no avail. He constantly bites us, legs, anything he can get hold of. Never experienced one this bad before. Help!!