This is how Racing Point discovered Renault's illegal braking system

Renault have been disqualified from the Japanese Grand Prix results after the FIA determined their braking system to be illegal. They've ruled the braking system as a "drivers aid" and therefore Daniel Ricciardo's 6th place, and Nico Hulkenberg's 10th place is now void. Racing Point launched the protest, but how did they manage to find such a thing? 

According to Auto Motor und Sport, Racing Point managed to identify the case because of a personnel change. The engineer who flagged the problem up previously worked on Hulkenberg's car. The engineer switched teams during the summer break. 

Renault have until 10am local time in Mexico to appeal the decision on October 24. In a tweet, Renault confirmed they will announce their next actions within the time period set. 

...that the system was entirely legal under the FIA Technical Regulations, it was judged by the stewards that the system was in breach of the FIA Sporting Regulations regarding driver aid. Both Renault cars... [2/4]

— Renault F1 Team (@RenaultF1Team) October 23, 2019

...and the variability of the associated penalties in recent cases, @RenaultF1Team will consider its next course of action within the timeframe laid out by the FIA. [4/4]

— Renault F1 Team (@RenaultF1Team) October 23, 2019