Shares of Starbucks fell on Tuesday after the coffee chain offered fresh signs of its struggle to bring back consumers, saying its turnaround efforts “will take time” as its new chief executive settles in.

Starbucks' new CEO Brian Niccol has his work cut out for him. Tasked with reassuring investors that the company's coffee shops are still hugely popular in the U.S., Niccol also has to contend with baristas and hardcore Starbucks customers who say they want plenty of changes.

The firm's baristas have complained that they suffer from chronic understaffing, poor pay and benefits. They are also urging the company to allow them to ban aggressive customers from Starbucks stores