Usage of food-delivery apps is booming, but the Uber Eats, Grubhubs, Postmates and DoorDashes of the world need to take a minute to work on service, according to a new study by Zion & Zion, the Tempe, Ariz. marketing agency.

Zion & Zion surveyed 1,084 consumers who reported suffering problems with orders about a quarter of the time with app-based delivery. 

Wrong temperature and unacceptably late were the top two complaints at 28.4 percent and 27.5 percent respectively. But almost as often, main dishes (20.9 percent) and side dishes (21.4 percent) were reported missing or incorrect.

"If one in four times, there are missing fries, what good does that do to only get two-thirds of the food ordered?" said Aric Zion, study co-author and CEO of Zion & Zion. "They have got to work on reducing the frequency of these things."

Third-party services delivered some $10.2 billion in food in 2018, according to Technomic. In 2019, Second Measure, a Bay Area analyzer of purchase data, noted delivery-app usage grew with 26 percent of Americans saying they had tried such a service compared to 20 percent in 2018. 

As restaurants have outsourced delivery to apps, they lose control of the all-important customer experience.

Non-millennials who get messed-up orders expressed extreme frustration at the equally extreme rate of 61.2 percent. Millennials are 14 percentage points more chill when their orders are messed up.

Late orders that arrive cold may be the fault of the driver, but more often it is the restaurant that will get the angry email or call. 

Zion & Zion found that 40.3 percent of frustrated customers complain to the restaurant, about 10 points more than those who say they lodge a complaint to the deliverer.  

While the Tempe agency handles a few restaurant accounts, employees decided to research delivery apps because order issues were prevalent in their own lives.

Stringent quality control by both the restaurant and the driver, such as checking orders before they leave the premises, is just a start. 

"The fact is, you are not in a restaurant, because in a restaurant they can correct an order in five minutes," said Zion. "With a delivery service, do you wait another hour for them to fix it?"