Have you ever crocheted something, put a knot in it and then tried to take it out ?
If you put a knot in something and then try to take it out you might take some of the stitches out too.
I'm crocheting a cardigan and I was putting the back and front pieces together and in order to help align the front and back pieces together I tied it at one end and realized I was supposed to tie it at the other end so I tied it on the other end too (on the top and bottom). Later I figured I didn't need the knots anymore so I took it out only there was a short piece of yarn by the stitches so I tried to make it so it wouldn't come out. I don't think the cardigan will come unraveled on the very bottom where the front and back pieces are sewn together.