What is Article 16, and why has it been causing hassle?

TheJournal.ie's Brexit reporter Gráinne Ní Aodha and BBC Radio Foyle's Dominic McGrath (formerly of this parish) join us on this week's episode to examine Article 16, and why it has lead to problems in Dublin, Belfast, London, and Brussels. What exactly is its function in the Northern Ireland Protocol, and why was the triggering of it so unexpected?