I sew quilt with a brother (older embroidery machine) they are quite touch about the needle....I have found if the needle is dull and/or wrong needle for the fabric it will skip stitches like that. usually has nothing to do with the tention..may have to loosen it a bit.. make sure feed dogs are in down position i like to make several small stitches then extend my stitches to what ever longer stitch i want to use for the project. this helps to tie the stitching instead of back stitching..