Placed eighth in the World Cup heading into the event, Chaffer was hoping for a strong showing in the two-run Canadian meet.
She was 10th on her first run down the 1.45 kilometre, 16 turn course, but could only manage the 12th quickest time on the second run, dropping her to 13th place overall.
“It was a bit of a disappointing day,” Chaffer said.
“I was 10th after the first run and was looking to forward to moving up on the second run, however I didn’t drive well.
“It’s disappointing, but I learnt a lot and there will always be another race to make up for it.
Fellow Australian Institute of Sport scholarship holder, Michelle Steele, was one of the quickest out of the starting gate on both runs, but 17th and 12 fastest times saw her finish 13th.
After the three North American rounds of the World Cup, Chaffer sits ninth in the overall standings, with Steele in 17th place.
The event was won by German, Marion Thees, 0.17 seconds ahead of Canadian, Sarah Reid, with Great Britain’s Elizabeth Yarnold in third place.