The article says they fairly quickly tried to reduce speed once they noticed something was wrong. But due to a (UI?) mistake they only reduced speed for 1 engin

The article says they fairly quickly tried to reduce speed once they noticed something was wrong. But due to a (UI?) mistake they only reduced speed for 1 engine. It wasn't until 3 minutes later they finally fixed that mistake but by then it was too late. So they were unable to understand their own speed controls.