It can sometimes be tricky to

It can sometimes be tricky to determine where to begin the first full stitch of a row after the chain that raises you up to begin the sc or hdc. Try starting in the next stitch over for your first stitch and work your last stitch of a row into the top of the turning chain.

If you are doing that, get a different yarn and practice out the stitch pattern. If you don't have any biasing with a different yarn, then it could be that the yarn itself is overspun and biasing your work. This can occur in knitting and it might be the possible cause of your problem if you don't have any of these issues working this pattern with other, different yarns.