Can I-485 be expedited for USCIS Error

My I-485 (NIW) was not approved when a visa No was available from last Jun to Dec because of USCIS error (USCIS already admited). But they told me that they can process my I-485 when a visa No is available in the future. Now I am thinking to request USCIS to expedite my I-485 processing because they made mistake on my case. But I have no idea if it is helpful or not when priority date is ot current now. What is your idea?