I'm working on my second monkey sock and I found I had an extra stitch when I got to the end of the heel flap. Everything looks even and nice, so I just knit two stitches together and got on with turning the heel.
When I got to the end of the heel turning, I was short a stitch.
It turns out that I didn't have an extra stitch, I just misread the pattern. But I didn't realise that until I had frogged almost the entire heel flap.
Oh, well. At least the heel flap knits up quickly. :)