Amazon is scrambling to improve its coverage of the U.S. Open in the U.K. after being deluged with complaints.

The online giant bought U.K. rights to the tournament in April as part of its new gambit of offering live sports to Amazon Prime Video customers. It already streamed the Queen’s Club tournament, a Wimbledon warm-up event, in June, but its coverage of the far larger and more prestigious U.S. Open, which began Monday, quickly spawned numerous complaints over picture and sound quality, the inability to watch replays of completed matches, and “bizarre” camera angles.

More than 80% of customer reviews posted to Amazon in the opening days of the tournament gave the coverage just one star, calling it “woeful” and “very disappointing.” One customer wrote: “If I could rate this zero stars then I would!”

A spokesperson for Amazon said: “We are working with customers to address specific issues – we listen to all customer feedback and are continuously working to improve the service.”

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On Thursday, Amazon increased the number of completed matches available for catch-up viewing from one to six, out of dozens that have been played since Monday. More are expected to be added.

The overwhelmingly negative response to the coverage so far, however, is likely to cause consternation at the tech giant, especially as it looks ahead to providing exclusive coverage in the U.K. of the 37 ATP World Tour events annually from 2019.

The cascade of complaints and poor reviews on Amazon’s website ceased for a period when new reviews were no longer being accepted, leading to accusations that the e-commerce giant had deliberately barred access to prevent more harsh criticism. But the company said the suspension was due to a technical glitch that has since been resolved.

As of Thursday afternoon, 717 of the 877 reviews received gave the service a one-star rating, with one customer calling it was “the worst Grandslam coverage ever.” Complaints particularly continued to center on the lack of catch-up and pause functions, with customers pointing out that the U.K. is five hours ahead of New York, where the tournament is held, making evening matches in the U.S. watchable in Britain only by those staying up into the wee hours.

“If you’re going to bid on this sport coverage at least give people the option to watch retrospectively not ONLY live,” one reviewer wrote.

The service did pick up some positive feedback, particularly for its commentary team, including former professional players Jim Courier, Daniela Hantchukova, and Greg Rusedski.

Amazon announced in April that it had secured the exclusive live-streaming rights to the U.S. Open in the U.K. and Ireland in a five-year deal worth $40 million. The move was another step forward in the tech giant’s move into TV sports to attract new customers.