Thread continually breaking in lower looper needle

Question

Lower looper thread continually breaks. I have had this overlocker for some time now and have used it successfully on all fabrics, I have tried to thread,just the lower looper needle, both the looper needles and all the needles in order but no success, it makes just 2 or 3 stitches then the same thread breaks. Please help I am now getting quite desperate over such a simple thing. email----- [e-mail]