It took me a minute to see the one miter. If I weren't putting it in a show, I wouldn't bother to fix it... but since you asked:
I'm sure you've already watched this video:
https://www.youtube.com/watch?v=cNPOkcyrMSg
Jinny says the block doesn't need to be perfectly square. The trick is to line up the center of your border strip with the exact center of the block & then mark the 1/4" points on both your border & block. It looks like you may have needed to ease in a bit of the block in that section in order for your points to match up.