Porsche issues performance warning, supply chain affected, leading to production slowdown. Porsche's stock price has recorded the largest decline on record. Previously, this luxury car manufacturer lowered its performance outlook for this year, stating that a shortage of aluminum components may lead to production interruptions for some of its models. This German manufacturer now expects a maximum return on sales of 15% - previously an upper limit of 17% - and has lowered its revenue expectations and the proportion of electric vehicle sales.