Symptoms

Removed a field from smartobject, view and from form and on submit the form still is saying field is required. Checked validation rule and it it no longer part of the rule as well.
 

Diagnoses

Removing rules one at a time revealed there was a rule that was causing the error. After the change on smartobject, all the form rules
 

Resolution

Updating all the form rules resolved the issue, form can now save correctly