Sometimes even the feet that are supposed to be 1/4" are not. I'd measure the seams to make sure.
and
Some patterns call for a scant 1/4" seam. That can make a difference, too, in the outcome. :-(
I struggle with this, too, you see. I finally took a piece of painters' tape - the blue stuff that comes off easily - and marked 1/4" on my machine.
Hope this helps...