The 2015 merger between Kraft and Heinz created one of the largest food companies in the world. It had $28 billion in combined annual revenues and controlled dozens of food and beverage brands that for generations were staples of American households, including Heinz ketchup, Kraft cheese, Oscar Mayer meats and Planters nuts.

These days, however, the mega-merger is a mega-mess.

Sales and profits have slumped. After taking a $15.4 billion write-down in February and slashing its dividend by a third, the company reduced the value of its assets by an additional $1.22 billion last month. Securities regulators are looking into its accounting, and after an internal investigation uncovered employee misconduct, Kraft Heinz said it would restate its financials for 2016 and 2017. It faces numerous shareholder lawsuits. And after laying off thousands of people over the last four years, it announced more job cuts in the second week of August.

For the Brazilian-based investment firm 3G Capital and Warren E. Buffett’s Berkshire Hathaway, the deal has so far been a rare — and costly — misstep. While their earlier acquisitions have produced big returns, the Kraft Heinz deal has created billions of dollars in paper losses. The company’s stock has plummeted 51 percent in the past year. Last week, 3G sold more than 25 million of its Kraft Heinz shares, bringing its stake in the company down by almost 10 percent.

Some analysts and former Kraft Heinz employees place much of the blame at the feet of 3G and its use of a highly vaunted “zero-based budgeting” strategy that critics say focuses more on cutting costs than creating products that people want to buy.