The nightmare year for Kraft Heinz continues. Shares of the troubled food company fell 4% Tuesday after Kraft Heinz (KHC) reported that its second-largest investor, private equity firm 3G Capital, sold more than 25 million shares Monday. Kraft Heinz said in an SEC filing that 3G sold the shares at a price of $28.44 on Monday, 4% below its closing price of $29.62. The company said in a statement to CNN Business that the 3G sale was “driven by periodic liquidity windows by 3G investors in the 3G fund that holds Kraft Heinz stock” and noted that this fund has made similar sales previously. 3G still owns more than 245 million shares in Kraft Heinz, about a 20% stake in the company. “3G remains a committed long-term owner of the company and has no current plan or intention to sell any additional shares,” a Kraft Heinz spokesman told CNN Business. The spokesperson added that 3G co-founder and Kraft Heinz board member Jorge Paulo Lemann personally bought more shares Monday. Lemann, according to the statement, said he bought more stock in Kraft Heinz “because I believe in its potential for a turnaround, and plan to hold this investment for the long run.” 3G was not immediately available for additional comment. Kraft Heinz has fallen nearly 35% this year, making it the fifth-worst performer in the S&P 500. Huge problems still lie ahead The company has faced many challenges, including accounting issues, the resignation of its CEO and a slide in sales and earnings as people look to eat fewer heavily processed foods and embrace plant-based products from the likes of Beyond Meat (BYND) and Impossible Foods. Kraft Heinz has been slower than many of its other traditional rivals to try and branch out into newer categories. General Mills (GIS) bought organic mac and cheese maker Annie’s in 2014. Hershey (HSY) acquired SkinnyPop maker Amplify Snack Brands in 2017 and also bought the maker of Pirate’s Booty from B&G Foods last year. And ConAgra (CAG)scooped up Pinnacle, owner of Smart Balance and the Udi’s brand of gluten free food last year. The rise of Amazon (AMZN) and Walmart (WMT) in the grocery business isn’t helping either. Those two retailers, along with Target (TGT), have put significant pressure on food companies to lower prices. That hurts the food maker’s margins. Kraft Heinz said last month that its revenue for the first half was down almost 5% from the same period in 2018 and that earnings were down more than 50%. The company had delayed its results due to an internal investigation of its accounting practices as a result of a probe by the Securities and Exchange Commission. The company completed its internal review in June, but told CNN Business Tuesday that the SEC investigation is ongoing. Giant writedowns on big brand names Kraft Heinz shocked investors in February with a $15 billion writedown of its Kraft and Oscar Mayer brands. The company followed up that news in August by reporting that it was writing down the value of more of its poorly performing brands, including $474 million in charges tied to Velveeta, Maxwell House, Miracle Whip and three other brands. It also took a $744 million charge after lowering sales forecasts for several of its international businesses. And the company slashed its dividend by more than a third earlier this year. Kraft Heinz’s new CEO, Miguel Patricio, who joined the company in July, has vowed to get Kraft Heinz back on track by focusing on innovative new products and less on cost cutting. Patricio, who replaced former CEO Bernardo Hees, was formerly a long-time executive at Anheuser-Busch InBev (BUD), another company controlled by 3G. “The level of decline we experienced in the first half of this year is nothing we should find acceptable moving forward,” Patricio said in a statement last month. “We have significant work ahead of us to set our strategic priorities and change the trajectory of our business.” Kraft Heinz’s woeful performance is also hurting Warren Buffett’s Berkshire Hathaway (BRKB), which is the company’s largest shareholder, with a nearly 27% stake. Berkshire’s shares are up less than 3% this year — well below the gains of the broader market.