Duplicate UTR on partnership that has ceased trading

Our partnership has ceased trading but we received a Self Assessment notice this yr with a duplicate UTR number, unknown to us these have been issued for the last few yrs! On ringing the helpline, we were told that this was an error, we should not have 2 UTRs and the accounts need to be merged. When contacting the helpline to follow up, it seems that the wrong account has been merged - the one with all the records into the one with past records, an old address and with a self assessment issued for a business that is no longer trading. Today, 9 weeks later we have been told there is a backlog. We can't request change of address to receive updates as was told it would cause issues so won't receive any correspondence. Similarly, if we register the duplicate UTR to see what's happening with this account in our government gateway will it cause issues / trigger penalties? Any idea what is a reasonable time period to expect the correct removal of the duplicate UTR before the self assessment deadlines/penalties in Jan? Much appreciated in advance for any advice.

Hi mcsd,
The nominated partner should contact HMRC at our Self Assesment helpline for an update:
Self Assessment: general enquiries
If you explain that you feel that the wrong records was removed, my colleagues can check this for you.
Thank you.