This is why both Russell and Kubica dropped out of the Russian GP

George Russell went into the barriers under the safety car in Russia. It initially seemed to be a problem with the brakes. Soon after, Robert Kubica was told to come into the garage to retire from the race. The team have since added an explanation. 

"We found an issue with the wheel nut retainer on George’s car, which led to the front-right wheel not sitting perfectly," said Dave Robson, Williams Senior Race Engineer. 

“This caused a lock-up under braking. The design is very mature and well-proven. The remaining inventory will be inspected thoroughly, and we do not anticipate a repeat of the issue. Unfortunately, we were forced to retire Robert’s car due to the amount of accident damage we sustained in the Singapore-Russia back-to-back races in order to protect ourselves going into the next events.

"The team has worked extremely hard to ensure race quantities have improved ahead of Japan and the final races.”

Kubica and his sponsor, Orlen, were therefore unhappy about the team. Kubica was quick to point out how he wanted to finish every race during the 2019 F1 season, but that can't happen now. 

The Williams car is progressing, but very slowly. The fact that the team are taking cars out of the race to save parts for the upcoming races is rather eyeopening.