Thank you all for your suggestions. I do load the fabric length of grain into machine. My fabric has a half an inch extra over die cut lines. I have looked at all of your suggestions and checked. The only thing left I thing is the die itself. I had a 5" square die that I discovered was off by 1/8" inch. It measured 5 x 4 7/8" as opposed to 5 x 5. This is a double stack half square die.
It measures 4 1/2" wide by 10 3/8" long, including the seam allowances.

I have not tried the paper trick. I will cut another set of triangles later today and use the paper to see if it helps. Will let you know if it does.

You can cut just the paper to check the exact measurement the die is cutting. If a true measurement then it's the fabric stretching, old mat, or could be low quality fabric. Usually it's the old mat that messes me up. Just like a rotary blade, the mat has to be changed after so many cuts.