I’m seeing the same problem here and I guess I created a duplicates issue here: Error creating “shadow” customer with two-legged authentication
I guess I will try creating an access token for this user and claiming a device to see if the customer shows up in the dashboard after that. I will probably try passing the scope=create_customer parameter as well to see if that fixes the original issue.
Is it confirmed that the scope value is required? Is there a way to make the make it a bit clearer or the behavior more clear? Seems weird to get a BadRequest but the customer is still created somehow.