BBC America Releases Orphan Black Season 4 Bloopers (video)
Just because you're a two time Emmy nominated actress doesn't mean you don't make mistakes every once in a while.
Though, considering Tatinna Maslany plays over 5 different characters on the show (Sarah, Helena, Alison, Cosima, Rachel, MK, Krystal, Beth...etc), it's understandable that she WOULD mess up. Being a clone is hard work.