Like most live recordings, anything can happen. Towards the end of MASC's performance (2:47 mark) when the boys ironically say, "Let me break it down", the camera suddenly shifted away focusing on the bright purple stage lights instead of the idol stars, causing the screen to show purple lights instead of the performance for nearly 3 seconds.
Seeing this, viewers were left confused. Fortunately, 'Music Bank' was able to quickly recover from the slip-up and things went back to normal, just in time to capture MASC finish up their performance.
It's reported that a KBS executive is currently in charge of directing 'Music Bank', filling in for the normal producer due to the ongoing KBS strike.