Red Bull have explained that Max Verstappen ended Friday's second practice session for the Sao Paulo Grand Prix early because the team were no longer gathering useful information from his long run.
According to Motorsport.com, the four-time world champion headed for the pitlane with just over six minutes remaining. Team radio suggested the decision came at his own request, with stand-in race engineer Tom Hart telling him he could box at the end of the lap.
Hart is once again deputising for Gianpiero Lambiase this weekend.
Red Bull head of race strategy Hannah Schmitz said afterwards that the team had found numerous inconsistencies during the long run and had already identified the changes they wanted to make overnight. "We weren't getting the data we needed," she said.
The early finish meant Verstappen missed the chance to perform a practice start on the grid. Motorsport.com noted this was significant given that the grid at the Autodromo José Carlos Pace climbs steeply uphill and Red Bull's starts have not always been strong this year. Mechanics were seen working underneath his RB22 once he had climbed out.
Verstappen finished third in both Friday sessions, around two and a half tenths behind the pace-setter each time. Lando Norris led the first session and Kimi Antonelli the second.
His day was not trouble-free. In the opening session he again raised concerns over downshifts, and a power steering problem made the car physically demanding to drive towards the end.
Despite the issues, Schmitz said there was considerable potential in the car and optimism for the rest of the weekend, with both drivers having areas they wanted to adjust. Verstappen arrives in Brazil having won three of the previous four Grands Prix.
She added that the top teams had tried all three tyre compounds because they are so similar, but warned that Friday's conditions were quite different from the forecast for Sunday, when changing temperatures and possible rain could make the data harder to apply.