Hi ..Mine did the same. even though I had substrate in the enclosure..What I did was add more in that area where she could dig down a little deeper and it stopped. I have not heard her scratch the sides since.
Morla did the same thing just before she feel asleep. it seemed like she was making it like a bed for herself. She is finally sleeling in her hide for the first time tonight, but I switched enclosures today. do you have a hide for your little one?
Peanut does that no matter where she sleeps and no matter what she is on, if she is on the coco, she only digs enough to make little piles around her, but it is always in a corner.
Mine does it too he is about 4months.
I have coco coir in my terrarium, he loves it. Even when I let him roam on the carpet he finds a corner and just tries to climb or dig.