Al mejor mono se le cae el zapote.
The sapodilla, locally known as the zapote, is a large, sweet fruit. Monkeys love them. But even an able-handed primate has been known to drop one from time to time. Hence, this is the equivalent of, “Nobody’s perfect.” For example: “Este desacierto pone en evidencia que al mejor mono se le cae el zapote, que somos humanos y nos equivocamos.” OR “This miscalculation makes it clear that nobody’s perfect. We are humans and we make mistakes.”
For more dichos like this, check out Lee Jamison’s Nicaraguan Spanish: Speak Like a Native.