A few things to make sure of. 1) the measurement of your lines of sewing. If you draw them first, make sure you don't mark hard as you can stretch the fabric - you are marking on the bias. 2) If you don't draw them, make sure you know where your 1/4 is on your machine. Make a test block and measure - are the two lines one-half inch apart? 3) This method calls for you to cut the blocks finished size plus 7/8 - that's a hard measurement to get exactly right. I prefer to cut them finished size plus one full inch, then square up as mentioned above. AND when squaring up HSTs, make sure your 45 degree line on your ruler falls exactly on the seam to ensure that the seam goes right to the corner. I can see that some of your seams don't go exactly to the corners and this could be the result of any number of things, either cutting, sewing or pressing. Keep going - we all have been where you are!