There's a good chance you may be lining the triangles up incorrectly. I also use the Tri-Recs ruler when piecing the Triangle-Square block, as it allows for more precise placement. I'm attaching a couple of photos of what it looks like when I line up the first piece, and how it should look when it's pressed open. Notice that the seam does NOT go right through the point, but is 1/4" away. Then when you sew the Triangle-Square block to the Four-Patch unit, the point will have that 1/4" breathing room that you need for the seam allowance. Hope this helps!
Andi