Actual GoodsIssue date not updated

Hi

We have a problem in Actual PGI date. For few documents system is not populated the actual PGI date in it's field, later we are able to complete the billing etc.

This is only an incident. What will be the reason, why it is not populated, what will be the data we can check for it, let me know at the earliest.

Thanks in advance

Venkat.