I made this Ozark Star pattern a few times & didn't have any issues. Is this the pattern you are using? http://www.fonsandporter.com/article...per_ozark_star

The finished size of the triangles are the same as 1/2 of the finished size of the diamonds, but the triangles have to be cut with a seam allowance added to make up for the difference of sewing two "half-diamonds" together. Is that your issue? The unfinished size of the triangles have to be bigger than if you would take one of the unsewn diamonds and cut it in half. (I don't think I'm explaining myself very well.) It's like taking taking two half-square triangles to make a square, you have to add for that center seam allowance to the triangles so they will finish the size of your square.

I was using the Fons & Porter pattern. In the future I will cut the strip for the triangles 1/4" wider.

The thing is everything lined up until I pressed the seams. Seam open, seam to the dark side - didn't matter. The triangles are 1/4" too short.

Except for that I like the pattern.