The initial purchase of two chairs involved an identical warped board/slat on the back of each chair. 
The handyman who assembled them let me know after the chairs were done and packaging materials disposed of.

I contacted Wayfairvand true to their promise of great customer service, they arranged to send for two repair/slat replacement kits to be sent.  When it was determined those were no longer available, Wayfair sent two replacement chairs!  The handyman assembled the chairs Saturday, and there were no flaws.  Thank you Wayfair!