Phew! Uber probably thought things were turning a corner after founder Travis Kalanick pledged to address that was described in a now-viral essay by a former engineer. But hey, when it rains it pours, and it’s pouring at Uber’s HQ. I mean, goddamn. Two early investors wrote an open letter to the company and , “We feel we have hit a dead end.”

Investors Freada Kapor Klein and Mitch Kapor that expressed vast concerns about the company’s internal probe of the allegations made by former employee Susan Fowler in an essay published on Sunday. They are, to put it delicately, not pleased:

By now a staggering number of people recognize the name of Susan Fowler and have read some account…

We are disappointed to see that Uber has selected a team of insiders to investigate its destructive culture and make recommendations for change. To us, this decision is yet another example of Uber’s continued unwillingness to be open, transparent, and direct.

Eric Holder has been working on behalf of Uber since at least last June, when he and his firm were to advocate on behalf of Uber to lawmakers concerning using fingerprints as part of background checks on drivers. Arianna Huffington has held a board seat for about a year and is deeply invested in the company weathering the PR crisis. As the company’s Chief Human Resources officer, Liane Hornsey reports to Travis’ executive team. This group is not set up to come up with an accurate analysis of the culture and a tough set of recommendations.

Holder pushed back in a statement with his partner Tammy Albarran obtained by , saying they’ll conduct a thorough, objective investigation.

“We are conducting this review with the highest degree of integrity and professionalism,” .

Still, it is extremely uncommon investors to react in such a public display, especially in the tight-knit alien fortress that is Silicon Valley. The couple said they’re speaking up because they’re “disappointed and frustrated; we feel we have hit a head end in trying to influence the company from the inside.”

But the couple has a record of looking to diversify the valley, so it’s not a tremendous surprise to see them expressing outrage. In 2015, the couple announced they would be to an initiative to diversify the tech industry. Kapor Klein and Kapor oversee several philanthropic organizations, such as Kapor Center, and they’re all in operation to increase diversity in Silicon Valley, according to the , which profiled Kapor Klein last year and described her as an entrepreneur and activist for workplace diversity.

For now, though, they’re not giving up hope on Uber and Kalanick, its brazen 40-year-old CEO.

“If we believed it was too late for Uber to change, we would not be writing this, but as investors, it is now up to us to call out the inherent conflicts of interest in their current path,” they wrote.