SEarch string: EBS customer number found but not posted during loading

I am doing configuration for an EBS implementation in development system. I have a search strings to look for the customer number in the tag 86 of MT940. in my search string saved search string defined as “virtual” S A # # # # # # # # # # # # # the customer number are found between 9th to 15th character in the configuration: it work when I used t.code: FEBST, the system identified the partner number/customer number. i have updated the following search string with Cocde: house bank Account ID external transaction; NTRX posting key: + integration: 000 search acct: virtual target field: account number active; checked mapping prefix: blank partner ID: blank posting rule: NTFX mapped to posting rule: 1511 Posting area: 1 posting key: 40 special GL: Blank Acct Debit: BANK compression; unticked posting key: Blank special GL: Blank Acct Credit: Blank compression; unticked Document type; ZR posting type: 8 whenever I load the bank statement, I got an error that the customer number is not updated when trying to find the customer to clear the open items. I have tried loading the bank statement with a BDC session created, the BDC session stop at error trying to update the customer number which has earlier identified in the search string. What am I missing?