How to unlock the attachments on an unlocked, signed form?

Our office is using a PDF fillable form that requires one digital signature. These are submitted by university students and the digital signature is from their faculty advisor. We have asked the advisors to not lock the forms from further editing because our office completes other data fields. Almost always, the student's form will require minor revisions from the student. Since the form isn't locked, this works fine. We don't require the advisor to sign again.

However, we also require supporting documents to be attached to the form. Almost always, the students need to revise their attached documents. Once the form is signed, we find that the attachments are locked. Attachments can't be added or deleted from the locked PDF. Can we set our form to allow the attachments to be edited even after being signed?

Or, how can our office remove the digital signature so the students could edit their form, including the attachments, then get a new signature? Thank you in advance!