U.K. government admits some offenders may have been wrongly sent back to prison after defective ankle bracelets alerted authorities that they had been tampered with. G4S blamed the problem on a manufacturing defect in 115 tags, or about 1 percent, had faulty straps. The company went on to say it had rectified the problem and the faulty monitoring devices posed no risk to the public British politician Tim Farron called the issue a colossal blunder”]