Carolyn, I am by no means an expert and have never used that ruler. But maybe double check to make sure that you are cutting the strips accurately, or something I'd do, make sure you are using the ruler correctly, I tend to not use fancy rulers lol because I can never line them up correctly, ok personal deficit here, but maybe double check that you are lining your strips with the correct line on the ruler. Hope you get it figured out.
vb. I am not sure I like the string blocks look either...I have never done a scrappy quilt before and not sure about that step. I did a string block type before but with all strips the same size and not randomly picked, so I can see I might struggle with that step. But I haven't even started with clue one yet as I am on the road heading home, and figure by the time I get those finished I may know the destiny of these string blocks and maybe change them to my taste or else see that I like them and go ahead with them. Maybe make a couple and see if you like them this time around? Or I like your idea of just squares or skip this week until you find the destiny of these string blocks and just make up your own thing?