Jonathan Knight, one of the members of the New Kids On The Block, walked off stage during a performance at New York City's iHeartRadio on Thursday night.
Twenty-five minutes into the concert, and during the ballad "Survive You," Knight appeared confused and uncomfortable, US Magazine reports.
"At one point, he appeared to be looking at his cellphone in the middle of a song. Knight was supposed to do a solo, but when it came time for him to sing, he couldn't get the words out."
Knight has been quite open about his struggles with anxiety. In 2001 he told Oprah Winfrey about feeling "trapped."
"The whole New Kids thing was crazy. The more it grew, the more I just felt like I was trapped. I just always had this feeling inside me of always being nervous and afraid of situations," he explained.
Knight later tweeted "I’m sorry..." and was back in full swing during a Today Show performance on Friday.
NKOTB are currently on tour in support of their new album 10. Last week the guys jokingly told Alexa Chung that this new tour was "mid-life crisis" reunion.