Wimbledon organizers have apologized and explained that “human error” was the reason behind the electronic line-calling system being turned off during a match on Sunday.

Russia’s Anastasia Pavlyuchenkova has questioned the bias of the officials at Wimbledon after controversial calls during the fourth-round contest against Britain’s Sonay Kartal.

CENTRE COURT, THE ALL ENGLAND CLUB — Anastasia Pavlyuchenkova suggested her British opponent may have received preferential treatment as simmering tensions around Wimbledon ’s use of electronic line calling (ELC) instead of line judges boiled over Sunday, when the technology malfunctioned at a crucial point on Centre Court.