Is this a new serger? Or one that you've had for awhile?
Are you by any chance pulling on the threads when the needle breaks? If it's an older serger, I wonder if the timing has gotten off because of the needle breaks. Timing would need to be fixed by a technician.
I would probably change both needles, completely unthread the machine, clean and oil it, and then re-thread from scratch. For the tension knobs, I put them on the lightest tension when threading (0-1) to make sure that the thread seats properly between the tension discs. I am careful to change those settings to the middle (3-5) before doing a test sew.
It isn't just the tension settings that affect the loops. The stitch width (moves the knife left and right) will affect how the loops hang off the edge. Also, you need to check if you have it set for a narrow bound hem.