Toverly has a good suggestion.
I think it is the tension of the fabric with the needle in it. When you turn or stop or pivot, you are putting pressure on the fabric. Sometimes you can't even see that it is stretched. So when I stop with the needle down and re-position the body of the quilt, I make sure the part that is under the needle is not stretching and has plenty of play before before lifting the needle again.

Oops, I was referring to using a metal open toe foot when doing applique like when machine stitching down a Dresden Plate; where you stop and pivot. A plastic foot has more tendency to slip. I see now you were talking about machine quilting, not machine applique.

At the points that you are changing direction, I make a tiny second stitch, almost like a lock stitch. It's usually so tiny that it's not visable, and the point of change looks clean when you go back to your original stitch length

This board is so good!! I just experienced this for the first time with a baby quilt I just finished. Sometimes my thread would snap too. I am definitely going to do the backstitch!
This is not the first time I have had a dilemma and surprise there is a thread pertaining to my exact problem!

After I pivot, I drop the pressure foot. and before I stitch, I lift the needle to see if the fabric moves. Then I can adjust.
I think this is a factor with all machines that do zz,or embroidery stitches, because the needle position isn't fixed.

Be really sure there is no tension in any direction on your fabric before you start again. Even a little tension will cause the fabric to pull a bit and give you that little "jump".

Watson

Also check that the fabric tension on your needle, rearranging your quilt can pull the needle a bit to the side, when you take a stitch the needle moves back to it's true position. This can break your thread too.
The sugestion to back stitch would help with this too.

Hope I did not confuse the issue

Karen

Great ideas! I have used my needle up/down button to see if the fabric moves after a pivot and if it does then gently guide it back so the needle falls in the same place before I proceed. Not the fastest way to do things but it works. I'll have to try the back stitch technique.

Yes, MaryKatherine, this is the right way to do it. Look and see if the fabric moves when you raise the needle.
If it does, you can then adjust the position before the needle goes back in. I can't figure out how a back stitch would help anything. If the needle is in the wrong place, only moving the fabric will solve that.