Bps dig sometimes.
What is your substrate? Do you have adequate hides? Not only hot and cold, but do they make the snake feel secure, tight fitting and low on the top? If those are off, the snake might dig more. Then again, your bp might dig anyway....
My Pinstripe will move his substrate around, but I wouldn't consider it burrowing. He's a little jerk and loves to make a mess out of his tub. I thought by putting cypress in there he would stop, but I come back the next day and he's got ALL the cypress moved from under his hide.