27-year-old Fanny Roos opened weakly in Walnut, California.
16.81 in the first round, and she did not bump over 18 meters until the fifth and penultimate round.
The Swede's best shot came in the final round - then the ball landed at 18.28.
It was only enough for a fourth place, third was the American Jessica Ramsey in 18.77.
Danniel Thomas-Dodd, Jamaica, won at 18.92.
Last weekend, Fanny Roos won the Triton competition in San Diego, California, at 18.99.
Before that, she opened the outdoor season with a third place finish of 18.64 in Portuguese Leiria.
On the night before Sunday, the discus duo Daniel Ståhl and Simon Pettersson - gold and silver medalists at the Olympics in Tokyo - will throw in the same competition.