At my project, we have some user stories which is either technical debt or tough story that PO and team cannot break down to smaller user stories by INVEST.(independent, negotiation, valuable, estimateable, small and testable). I know in the best case we should somehow find a way to break it down but in my case we cannot break it down.
So we have decided to keep it big and implement+test it around 2 sprints.
But my PO and his board management feel concern about it because: