FRANKFURT—Premium car brand Audi, Volkswagen’s biggest profit contributor, has to troubleshoot on a day-to-day basis to tackle an ongoing shortage of auto chips, its chief executive said. “We had a very strong first half in 2021. We do expect a much weaker second half. We really have trouble,” Markus Duesmann told Reuters ahead of the Reuters Events Automotive conference, calling the situation “a perfect storm”. Duesmann’s comments highlight the problems global carmakers are facing in navigating a global chip supply crunch that has hit car production around the world. But while the car industry’s vehicle sales have suffered it has softened the blow through price increases that have boosted margins. Audi in July said it had been unable to build a mid five-digit number of cars in the first half of the year. But its profit margin in the period surged to 10.7 percent, even surpassing the 8 percent in …