There has been some arm wrestling with my spinning wheel. In due course, resolved with a new drive band, then a shortening of the drive band, and replacement of a tension spring. Until then plying was doing me in every time. This three ply sock yarn was the bitter end. I hated it. Three ply yarn is a lot of work, and you want it to look great and function well when finished. You do NOT want the plying, the final stage, to ruin it. In the end I fixed this situation by putting it through the wheel a second time and adding some twist to even it out.
And… there has been more spinning… the sock yarn is merino lamb and the yarn below is some local lawn mowing wool–not too soft but sure to come in handy for something that does not require next-to-skin softness.