New field not saving to database.

I created a new field in Service Header (ID: 5900). This field has a type of Option. When I add the field to the Service Order Page (ID 5900) I can select a value and click ok and the value persists. However, when I add the Field from Service Header to the Service Item Worksheet Page (ID 5906), the selected value will not save to the database.

In the Service Order Page if I leave the prefix ServHeader."New Field" it will not save. Once i remove the ServHeader prefix it will then save.

My questions are the following:

Why will my selected values not save when the prefix ServHeader exists in front of "New Field" on the Service Order Page, but when I remove it, they save?

Also, what am I missing in regards to referencing the ServHeader."New Field" on the Service Item Worksheet and why it won't save?

Thank you!