Nationstar may not be the only servicer facing surprise losses due to erroneous accounting practices.

Fitch Ratings recently claimed that confusion over how to account for principal forbearance resulted in $1 billion in surprise losses on mortgage bonds backed by Nationstar-serviced loans.

Now Moody's Investors Service is sounding the alarm as well, claiming Nationstar isn't the only servicer at risk. Indeed, the bad accounting may spread much, much further.

The credit ratings agency states the full extent of the risk is difficult to gauge as mortgage servicer practices are far from uniform.

"Among the primary servicers Ocwen (OCN), Bank of America (BAC), Wells Fargo (WFC), Nationstar (NSM) and One West report forbearance losses to the trust when they book the modifications, but others, such as Aurora Loan Servicing and Green Tree, do not pass the forborne amounts through as losses until they liquidate the loans," the Moody's analysts state.

In early June, Ocwen faced $1 billion in losses on 170 U.S. residential mortgage-backed securitizations due to losses from principal forbearance modifications enacted by the previous servicer, Homeward Residential.

"The trustee’s delay in reporting the forbearance losses in these transactions was due to the additional processing necessary because of the large volume of affected deals and to the approvals the trustee needed to obtain from other parties to the transactions," the analysts write.

Wells also confirmed discrepancies in some transactions and said it would report additional deferred losses as restatements potentially in its June/July remittance reports, according to Moody's.