One of my dog's is starting to get a little feral and at times can be uncontrollable. We have tried taking him to puppy school after I had a dog trainer come assess him at the house. He could only go a few lessons as every time he would come back from there he got a little bit more agressive; now it can get to the point where no one can change his clothes and give him a shower without him wanting to nibble. Please help!! We also have another dog who's so beautifully natured that we don't want one rubbing off the other in a bad way.