(Bloomberg) -- Two Sigma Investments disclosed that a years-long dispute between its billionaire co-founders is continuing to pose material risks to clients and affect its ability to keep staffers from leaving, with a 12-year veteran of the $60 billion hedge fund set to depart.   

Co-founders John Overdeck and David Siegel still disagree on the authorities, responsibilities and compensation for their own roles as well as a range of senior executives, including chief investment officers, the firm said in an updated regulatory filing Friday. Their rift also extends to how teams are structured, corporate governance and oversight matters, and succession planning. 

It’s affecting Two Sigma’s “ability to retain and attract employees (including very senior employees),” the firm said, adding that the “ability to achieve client mandates could be impacted over time.”

David Cohen, the global head of investor relations who has been at Two Sigma for 12 years, is departing in May for a new opportunity, according to an investor letter seen by Bloomberg. He is being replaced by Chris Busby, the firm’s head of growth and strategy for Europe, the Middle East and Africa. 

Co-chief operating officer Jeff Penney is stepping down from the role, and Tim Reynolds, with whom he shared the position, will become sole-COO, according to the letter. For nine months, the duo assumed the role replacing Jon Hitchon, who left last year. 

A representative for Two Sigma declined to comment. 

Last year, the quant giant first disclosed that a falling-out between Overdeck and Siegel had grown so strained that it amounted to a material risk to clients. Tensions between the two — who launched the firm in 2001 and are the only members of its management committee — were already affecting talent retention and the ability of employees to fully implement key research, engineering or business initiatives.

Two Sigma employed a consulting firm last year to perform “an exhaustive review” of its corporate design and governance framework, according to the investor letter. 

The quant giant also said in the letter that it’s been ramping up its focus on machine learning, helping it release a record number of models last year, and boost model complexity and productivity.

This year, Two Sigma’s biggest funds, Spectrum and Absolute Return Enhanced gained 3.6% and 6% respectively, through March 22, according to a person familiar with the matter. It’s smaller macro-focused Compass Enhanced fund is up 24% in that time. 

(Updates with review in eighth paragraph.)

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