How to restrict sales order submissions if a mandatory EFF field is blank?

Summary:

Sales orders should not be submitted if the mandatory EFF field has not been entered.

Now I am able to submit the sales order even though the mandatory field is blank.

But I get error whenever I navigate to the EFF and leave the mandatory EFF as blank. 

 

Can anyone confirm whether it is an a seeded behavior. 

 

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):