Fabric Tunneling or Rolling when serged?   

This is usually a combination issue of incorrect Tension settings, incorrect Differential Feed settings, or not enough fabric support with for thin fabrics...   (See also Differential Feed: Understanding and using the Differential Feed)   

This can also frequently happen when serging only one piece of fabric on an unsupported edge (see below, Washaway Wondertape)

The rolling usually happens when you have your tension too tight on a looper. I see your upper looper is on 7. That's a bit high. Try lowering that tension and moving your width back to the default of 5. Tip by Admin Karen Wood

Perfect Narrow Roll Hem On Sheer Fabrics With The Brother 1034d Serger

Is your fabric being pulling into the feed dogs as you serge?

Serging sheers and fine fabrics is a challenge, but it can be done. For finishing a rolled hem edge, or construction seams, on chiffon, lightweight knits, or slinky fabrics like lycra or spandex, rayon challis, sometimes the best trick is

Stabilizing Seams with Washaway Stabilizer