The controversy began on April 13th after the broadcast of KBS‘s ‘Music Bank’. During HyunA’s part of “Volume Up“, she was only seen dancing and not singing. Netizens circulated the screen capture through online community boards, beginning the controversy over her lip-sync mistake.
On April 17th, a Cube Entertainment representative explained, “There was a mistake as she had participated in multiple prerecording sessions for their comeback stage. We will be more careful to not have this same mistake in the future.”
Source: My Daily via Nate