Thanks for additional details.
Our Engineering Team would like to get your best contact number and preferred time for a call for the Fault Update.
Kindly PM me your best contact number and preferred time tomorrow.
This issue can now be closed. Changing over to UNID3 has resolved the issue - this indicates that both UNID1 and UNID2 on my NBN NTU is defective.
Thank you for resolving this issue so vigorously!