Hi Ron,
When saving a record it applies the dictionary validation to the whole record.
This is necessary because the backend will also apply validation to the whole record - not just the fields that are changing.
So when you update, or insert, a record all fields must have legal values - not just the ones actually on the form.
Use the priming tab, or the embed point you mentioned, to prime any fields which may, or may not, be on the form.
cheers
Bruce