Dropdown list is not updating correctly

Dropdown list is not updating correctly

I have a dropdown list that updates when another dropdown list is changed using scripts.  I've noticed that the update is only working selectively on some records but not all.  Why?  I have not thuroughly checked but it seems to happen on the records that I imported instead of manually entering into the db.
 
Please advise on this as without this working I cannot use my application correctly.  I will enable access to support.
 
Please check the "Division Orders List" form.  Try selecting a 'Lease" and then check the dropdown box below labeled "Well".  In some occasions it does not update.
 
Please advise