Biting and niping - bite inhibition
Grass riping - Out of frustration/anxiety. Lots of observation and studying his behavior went in to making that determination.
Resource Guarding - Without a common trigger, like teasing, competition, etc.
A thought here is that he might be a very energetic "busy" puppy. Grass tearing
- normal. Jacks is a shredder too. Not so much with grass (he grazes), but any toys he gets his mouth on when he's in one of his super-hyped-up moods inevitably gets shredded.
And our dogs graze all the time. We aren't golf-course yard people so we don't care. Nipping-biting
- normal. I'm sure you saw my comments before on what we went through with Jacks during his first year. He still is a very oral dog (he gets hyped up, he can't control his mouth). My mom would call me during the day, upset because I had brought home an aggressive puppy. One time she even had me come home from work and meet her at the vet. The vet raised an eyebrow and simply told my mom we were dealing with both a mouthy puppy and a teething puppy - who didn't have an aggressive bone in his body.
The other thing too is that when the dogs are bothered by something or want to go outside for potty, they tend to get a bit more mouthy and nippy. <- our pup right now is not nippy in the least (he was with his littermates until almost 10 weeks old), but even he will get extra fussy and mouthy when he has to go outside. Resource guarding
- that is concerning, but has various causes, including the puppies learning how to press their owners buttons to get their ways.
Make sure the trainers earn their keep to solve these problems. The fact that they worked with you for 20 hours and have not yet come up with a method to TRAIN The dog does bother me.