A-Z guarantee claim

I sell custom items. I had a person claim they never received the item. They have 2 more orders placed that have not shipped yet. I am afraid they will claim a-z for those 2 orders, should I cancel?

Their first order was for an item for themselves, they have not reordered but have ordered for other employees at their organization. If they didn’t receive it, wouldn’t they reorder? I am pissed that there is no recourse for buyers screwing over sellers.