I have had the same issue ad infinitum in the past, have used the new sponsor name and EIN, and noted Item 4 with the name of the prior year sponsor.
IRS has sent the client notices, which we have answered, they send another notice and an invoice from IRS for a delinquent filing mentioning we have not replied.
This has taken many months to clear up -with IRS Notices and our responses; and many irate clients.
Who do you think they blame - the TPA.
Recently we were informed that we should either send or fax IRS in Ogden, UT informing of the sponsorship change, enumerating old sponsor with EIN and new sponsor with EIN. Apparently Ogden is the one to make the change.
Perhaps this has worked as there have been no repercussions... or perhaps due to COVID (and the Hurricane Ida extensions), IRS is backed up.