OPTXT field (Text) is not getting updated after Installment plan

Dear Experts,

While making the billing, all the line items are getting updated with the Contract object text to OPTXT field.

But after executing Installment plan by t-code: FPR1 for any of the open line item, the OPTXT(TEXT) field is becoming blank and only BTEXT (Description) field is getting updated

Is there any way, where i can get the OPTXT field update for the executed line item by Installment plan.

Please help.

Thanks and regards,

Aditya Viswanath