Lots of assumptions here.
1.The staff followed standard procedure and informed the guest that his/her entree could not be prepared up to reasonable standards because of a problem.
2. The guest decided to order the entree even knowing that it would not be prepared properly.
OR
1.The guest received a poorly cooked item and DID NOT complain to the server or management.
2.The above happened, and the guest DID complain to the server.
3. If the second, management responded to that complaint by offering another entree, comping the item, etc.
The OP does not say that the third didn't happen. He might still have wanted to know the reason behind it happening in the first place - especially in a brand new restaurant. He also did not state if the first happened. So people don't have enough information to criticize the guest for lack of common sense, or management for lack of customer service.
It appears to be faulty equipment, which is not necessarily WDW's fault. But it could be, if it is a result of user error, lack of maintenance, etc.
There is also the possibility that due to allergies or just personal taste, there was nothing else on the menu that the guest either could safely eat, or wanted to eat. Maybe this was a "safe" choice that had been fine in the past. There are sometimes hidden ingredients that can be avoided by ordering something grilled, no sauce or spices, please. So the guest took a chance that it wouldn't be all that terrible tasting rather than not eating at all. And lost.
