USCIS has issued the following press release re: the reissuing of I751 extension receipts.
On Oct. 16, 2018, USCIS began issuing new receipt notices for certain Forms I-751, Petition to Remove Conditions on Residence, to replace previously issued receipt notices containing inaccurate information. In August 2018, USCIS issued receipt notices for certain pending Form I-751 petitions to extend conditional permanent resident (CPR) status from 12 months to 18 months. These receipt notices were issued to provide an additional six months of CPR status to the I-751 petitioners while they continue to wait for their petition to be adjudicated. Some of the receipt notices contained incorrect information that does not affect the extension of the of the CPR status. Petitioners who received incorrect receipt notices will receive corrected ones shortly. If you have not received a corrected receipt notice by Nov. 15, 2018, please reach out to the USCIS Contact Center.