I've posted before about my puppy having trouble learning "no" and "leave it", and his biting issue. I've been training him consistently for months after we got him, and at 6 months later he's still destructive so we can't have him out of the pen or crate to roam around unless he's being played with, we can't have him on the bed or play with him more than a few minutes because he goes right to biting, and, unless there's a treat in hand, he rarely listens to commands he follows almost flawlesdly otherwise.
For biting, I've been redirecting every day for months, isolating him whenever he bites, the works. Isolation solved nothing, he just returns to the room (or i do) and he latches on. Redirection achieves nothing either, he'll actively avoid the toy to get your hand.
He only ever chews his toys when he's in his crate, and sometimes not even then. Various textures, kongs ( he doesn't chew them, only licks no matter how they're set up), and the only things he wants to chew are things he shouldn't like cardboard or plastic, or people.
I've watched hours of videos about stopping the biting and every dog i see already seems "good" and they just have a small nibbling problem. Mine has grown from nipping to full arm in mouth chewing. I don't want him to think its ok (not that he cares) so I can rarely play with him because he goes straight to biting. It's not aggressive biting, I can tell its teething and playing, but I still can't get it to stop. I'm at a loss.