I can't give you any explanations, but I can say I am very sympathetic. Don't have a lot of words of hope as I am still going through chewing with two of them, both over a year old. Mine are golden retrievers. They actually stopped for a while and it is like they are going through a second childhood because they have started it back up. The latest catastrophe is an ink cartridge for our color printer. One has a blue ear and the other a blue leg now. Don't even ask me what my rug looks like! Good luck. Practice a lot of patience.