ERROR MESSAGE WHIE CREATING BILLING DOCUMENT

Hello All

I m trying to create a billing document for a delivery. Billing document is created and I m getting a message as Billing document saved. but when I go back, I m getting a message saying "Update Terminated".

Then when I enter the billing document number that was created new, an error message pops up saying " Billing document does not exist".

but I could successfully create billing document for other deliveries.

Any idea why is this happening ?