Fields not stored if conditional field changes

Hi
I have 2 issues and I know that it is linked to a conditional field.
I have an online exam paper and give the students a code to enter which will show the questions. On submit I will send a mail to myself with the questions and answers.
1. When I changed the conditional field (Exam Code) while the students are busy writing, their answers will be stored as blanks.
2. When I do a resend of the exam form and the conditional had changed, the questions will be send but with blank answers.
How can I overcome this?