Really cute quilt!!
I have a couple of questions - looking at the quilt I am thinking that you went from left to right and then sewed from right to left? Did you baste the sides first? Is is possible that your tension is too tight? On my LA, I baste the sides then clamp it. It is finicky as to how tight the fabric is in both directions . I get sometimes get that shift in fabric when basting if my tension is too tight so maybe it could be a combination of tension and direction. Are you using a Towa gauge or drop bobbin method to set the bobbin tension.