Error Unit list price is required on a booked order line

Hello Oracle Friends,

We are facing issue while re-configuring ATO item as below

Error:

Unit List Price is required on a booked order line

This only occurs if the calculate price flag - calculate price. If the calculate price flag = Freeze then the change can be made without error.

We have configured ATO item and Model Price populated.. and after someone attempts reconfigure to ATO item system tried to re-price the line and getting above error message.

Calculate Price Flag set to "Calculate Price". But earlier we never faced such issue though same setup and same process we are following.