BTS's "Pied Piper", "Go Go", and their two hidden tracks "Skit: Hesitation and Fear" and "Sea" have been deemed unfit for broadcast. "Pied Piper" talks about brands such as Twitter and 'V Live', while "Go Go" and "Sea" contain inappropriate language. The skit has lyrics that are beeped out, and could be confusing to the rules.
2PM Junho's songs "Nobody Else" and "Wow" were also deemed inappropriate because of inappropriate language, and "Run to You" was deemed so because it mentioned specific brands by name.
Similarly, iKON Bobby's "Up" was deemed inappropriate due to cursing and language.
Because none of the songs are title songs, it's unlikely that any of the songs will be resubmitted for review.