Overlocker problem.

Undo the pressure foot and cut away at all the excess thread above and below. You might have to lift the stitch plate as well . It does muck up whatever you’re stitching.

Raise the pressure foot and rotate the balance wheel slightly in each direction while gently pulling the fabric.

Yes, I’ve had this problem a couple of times and I just cut it away using a small pair of scissors and a seam ripper. It seems to happen if I try to sew something too thick or too fast.