AsNoriuanswered grow question 2 years ago i cant see were bana could grow, usually they form on much later stage of grow, balls can form any time.
Worst to worst , if its only plant in area and nobody growing him will visit, he can continue with monitoring new sacks, sterile way cut them off and hope for best. If best is worst - you can still do bubble hash and extract all the goodies.
I had few times one sack appearing at the start of flower but girls were finishing without any more issues ...
Happy Growing !!!