In my experience BPs don't do it because they want to explore. In every situation I've encountered this with BP's it has been because the enclosure was too big or temps were off. What is the height in this enclosure? Even more than floor space, too much vertical space really tends to trigger this behavior, though a 20g is already pretty tall for a 6 month old BP. It still throws me off because he seemed fine in it for a while, but it very well could be that the initial move freaked him out enough to stay as hidden as possible, and he has now gained the bravery to try and escape to a more suitable environment. It may be worth just putting him back in his old enclosure to see if that makes the behavior stop, but before you resort to that, I'd go ahead and try to add a lot more clutter to see if that is good enough for him to calm down. You want almost every part of the floor covered with something he can be hiding in rather than spots that are bare and he feels exposed.