Account; changing Account Classes whilst a Quote causes issues once opened

If an Account is changed from one Account Class to another whilst a Quote it may cause issues once opened.

For example, create a Quote Account for a Fixed Term Loan, edit and change to a Revolving Credit Loan and open. On the Financial page an error will now appear with the description "Failed to load Account Calculation.".

Note, this occurs because some fields unique to one class were not cleared when changed to another class.