I'm working on my first log cabin now. While I like the look and I'm chain piecing I still find it a terribly tedious process. I trim each strip after it's added since I'm chaining and need to cut each block off the main strip anyhow.
My thinking is that if your beginning and ends are off on each log/side that you may be skewing your strip as you are sewing. It might help to stack a few post-it notes at the 'scant' 1/4" measurement from your needle (if not able to reposition needle on your machine). But your fabric up to the edge of the post-its and you may get more consistent seams the length of your block.