RESIGNMENT OF FUNCTIONAL AREA TX FMN0

Hi, I am running transaction FMN0 with some FI documentes to reasign Functional Area in Budget Document through FMDERIVER. While most documents are reasigned fine, I am getting 2 types of errors in others:

Error 128:

Document not updated, it already exists or is not relevant for FM

Error 057

System error: funds management commitments interface (FISTL, FM_DOCUMENT_CHECK_DATA)

Please help.