Starliner's flight to the ISS was much more harrowing than originally thought
(arstechnica.com)
Essentially, Wilmore could not fully control Starliner any longer. But simply abandoning the docking attempt was not a palatable solution. Just as the thrusters were needed to control the vehicle during the docking process, they were also necessary to position Starliner for its deorbit burn and reentry to Earth's atmosphere. So Wilmore had to contemplate whether it was riskier to approach the space station or try to fly back to Earth. Williams was worrying about the same thing.
Essentially, Wilmore could not fully control Starliner any longer. But simply abandoning the docking attempt was not a palatable solution. Just as the thrusters were needed to control the vehicle during the docking process, they were also necessary to position Starliner for its deorbit burn and reentry to Earth's atmosphere. So Wilmore had to contemplate whether it was riskier to approach the space station or try to fly back to Earth. Williams was worrying about the same thing.