Bill only lines not getting closed, status remains in "booked", What can be done?

Hi,

We had few scenarios where bill only lines getting stuck at line status "Booked". When we try to view the line workflow, a note gives the following message.

"workflow status is not available. The workflow history may be purged". What is the reason for this behavior? How can we avoid this behavior?

We are currently cancelling the lines and re- enter the lines when this problem occurs. But it's not practical. Please let me know what is the reason for this kind of behavior?

Thanks and Regards

Chathuri