Sporadic Budget Definition not found error during the ARUPDATE process (AR_UPDATE2 to be exact) duri

We are getting a Budget Definition not found error about once every couple of months. When we ask the user to un-post the invoices they just uploaded and do a re-upload of their invoices and run the process again, it works fine so we are not sure what is causing the error to happen. I do notice that the AR_CC_TRAN_TBL has a blank BUDGET_DT which is probably causing the error but there is a BUDGET_DATE in the PS_ITEM_DST table.  Somehow the data seems to get corrupted and the budget date suddenly goes  blank.  The app server logs during this time