By default, Adobe Analytics tracks referrer from document.referrer, but here it is not behaving like that, seems something is overriding, you need to check internal URL filters or check custom code editor.
You can override this using s.referrer plugin, for this, you need to write code in Adobe Launch custom code editor.
Example:
s.referrer=document.referrer;
If you are using Launch then you can use Adoeb analytics plugin code editor to place your custom code.