Free Motion Quilting Help

[hilrow]

Good morning!

I have just started practicing free motion quilting and giving the meandering stitch a try. The front looks fine but when I flip it over my stitches look like this. What is causing this?

When I first tried stitching my thread was coming out of the needle so I worked on the tension and it seems to be staying in there now but I would love to know what tensions work for other people. I have a Janome 4120, it's a brand new model but almost exactly the same as the 3160.

Thanks for any help or guidance!

Hilary