I recently had my pool deck covered with thin pavers. The original concrete deck was left intact, and the new pavers laid on top, then sanded.

It looks fantastic, but the pavers have movement when walked on. it's hardly visible, but you can hear the pavers moving. Also, when something is dragged across them (like the hose) they sound loose.

Should they have been mortared down? Do I have a legit complaint to the contractor?

We had the driveway done at the same time. The old concrete drive was removed, and full thickness pavers used. It's solid, no movement.