The following issue has been identified and subsequently replicated by MYOB Support in EXO Business versions up to 8.3.1.
Issue
Support have confirmed that when entering a batch of creditor invoices (so you don't close out of the invoice entry screen each time you enter an invoice) the detail entered in a URL extra field will remain after the invoice is saved and all other fields are wiped.
Any URL type extra field is not clearing when the invoice is saved.
Workaround
N/A
Resolution
Attached to Problem ticket 11996130775 for resolution. Issue does not replicate in current versions of Exo Business, and is closed.