German sandal maker Birkenstock earned less than expected in the third business quarter despite a surge in profits, the company reported on Thursday. The company’s stock dropped 11% in pre-market US trading, erasing some of the 32% gains made since the company went public on the New York Stock Exchange in October. From April to June, revenue rose nearly 19% year-over-year to €565 million ($626 million), Birkenstock said in a statement. “We achieved the highest quarterly revenue in our history, driven by unbreakable and growing demand across all segments, channels and categories,” said chief ex…