Wiz was very attached to computer games. Even if he was not allowed to play them, or he had no access to a computer that would play the disc the game was on (back when we had the floppy discs) because we had upgraded and the game was on a different drive.
He even ransacked my parents' part of the house and took a laptop at one point. It didn't have a power cord or battery, but he STILL kept finding it no matter where they put it. He actually hacked out part of a box springs to hide it in. And it wouldn't even turn on.
I am sorry he is still hoarding the things that have been a problem. Wiz also hoarded food. He once hid a box of ice cream bars in the couch. All unwrapped.
Does the hoarding get worse when he is feeling stressed? Or the stress get worse when he has again accumulated things? Wiz would hoard more and more stuff when his other behaviors were out of control. If we got rid of them, and of the other stuff he obsessed over, we had about 2 or 3 weeks of total Hades, and then he would settle down for a couple of months. I knew when he started hoarding again because he would start with some of the other stuff.
Have you figured out where he is getting the stuff? What does the therapist say? It is such a tough thing to handle.