Pinning more might be the cure but when all else fails simply tack the intersections together and then sew.

What is the name of your fabric?

Looks like the triangular corner down from the problem is also not lined up. Perhaps it started below somewhere.

yay! Glad you got it now.

Can't wait to see the whole quilt. It is going to be beautiful. I used a hint from someone on here and tacked (with thread) the corners on my latest project and it came out perfect. I tried the three pin method but I hate dealing with pins when I'm sewing. If you tack with thread then you can just sew right through. I also pinch my seams per Jenny Beyer's advice. Get them between your fingers so you can feel exactly where they meet. And, I use the "peek" method too.

That corner is where you need to place the straight pin, and then the two securing pins.

I think when you do this, make sure that the pin is 1/4 inch in on the slanted seam and match up at 1/4 in in on the straight seam. Maybe you are matching up the edges of the fabric where the seams meet instead of at the seam allowance. Ann

When making your blocks do you square them up before you attach them together.

.Wow! This will be great for a newbee like me to try. Thanks so much.

I noticed first off that the print didn't match either so the problem is below the triangle.

I didn't want to use starch either, but OH does it make a difference! Pinning works too. I was worried about the holes, but it literally will "come out in the wash". The batting will plump up and fill in a lot of "errors".