(Bloomberg) — Tesco Stores canceled thousands of online grocery orders due to a systems glitch, leaving some customers empty handed in an embarrassingly timed slip-up for the U.K.’s largest retailer.

A fault with software used by Tesco workers to pick customer orders from its stores led to the cancellations, which the company said affected less than 10% of orders. Tesco is No. 3 in the 2016 Europe 500.

“We’re working hard to fix this problem and apologize to customers for any inconvenience this may cause,” Tesco said by email. It didn’t say when the problem would be resolved.

The breakdown comes as Amazon.com Inc.’s (No. 1) $13.7 billion takeover of Whole Foods Market Inc. highlights the growing role of technology in the global grocery industry. The U.S. giant is said to be considering the introduction of systems to eliminate cashiers in Whole Foods stores and trademarks approved last month also suggest that blueprint will be coming to the U.K.

Tesco’s systems fault is the second to hit Britain’s big grocers this month, after a recent failing at rival J Sainsbury Plc (No. 21) forced the company to delay or cancel deliveries from almost a third of its stores.