Error when changing the Earmarked Fund document in FMX2 Transaction

Hi,

We are following the Below process for  MRP Materials Procurement

Reservation-PR-PO-GR-IR, and budget check is there only at Reservation and GI Creations level;

when i am doing the changes to price in Reservation FM Document through FMX2 , Sytem is giving the below error.

we want to update new MAP price afer PO Releasing in Reservation FM Document.

After Selecting the Account Assignment Changeable indicator,

again below error is coming.

Thanks &  Regards

SAM...