See this from Eric Berger:

"Boeing and Rocketdyne more or less hated one another," one person involved in the test told Ars. "Everyone was in super-defensive mode even before this happened. It had been classified as a risk, but the two sides weren’t talking openly and honestly about it."

What was the source of the animosity? After Boeing selected Rocketdyne, according to sources, it asked for changes to some system specifications. This prompted Rocketdyne to ask for a change order fee, as is customary in government contracts. That infuriated Boeing, which thought it had a partnership with Rocketdyne, but the latter company saw itself as a contractor. As a result, the Boeing and Rocketdyne teams were effectively walled off from one another and did not iterate together toward a more effective propulsion system.

https://arstechnica.com/space/2024/05/the-surprise-is-not-th...