Release billing documents for accounting issue

Hi experts;

    While the key user was processing the VFX3 to release some sales orders he received the attached error.

Actually, I'm confused littler bit about such error and I cannot get the main point of the problem whether it is an SD issue, CO issue (because it talked about the Cost Estimate) or MM issue.

So may you kindly advice and guide how to solve and understand such issue in some more details

Thanks in advance,

Kind regards;

Ahmad Mahmud;