Could be when you start the row your stitches are looser. For neat even stitches at the edge, I do the first stitch, then pull the yarn a little and work the next couple sts a bit tighter. That keeps the end sts from being loose.
It's curious that the looseness only happens on one side. I like to slip the edge stitch at the beginning of each row. This works well if it's an unfinished edge and if you need to pick up sts along the edge, it makes it all much easier.
This has happened to me over the years in knitting and may be because of the stitch pattern. if you do the first stitch then pull the yarn a bit and focus on making the first few a little tighter, it should do the trick