Help! - Juki HZL F-300
 

I have a new Juki HZL F-300. I am sewing a straight stitch using the automatic thread cutter. I have checked the threading on both the thread and the bobbin numerous times. I have changed the needle several times.
Issue: the threads nest at the end of my seam. Both threads cut but the thread somehow threads itself through the fabric twice and I end up with a tail. So every time I start a seam there is a long thread from the thread itself.
I hope I explained this well. Does anyone have suggestions on how to solve the problem?

Use a leader. That is, a small piece of waste fabric to start your seam, then sew off onto your actual seam.

A photo would help

I have an F600. Yes, that is the way the cutter works. I often use it during my quilting. Then I have to go back and cut off those tails. I just consider it part of the process. Come to think of it, I had a different machine with a cutter, and it did the same thing.

Just a thought. . . When I use three of the upper loops to thread my machine, my needle unthreads when I use the cutter, so maybe the number of upper thread loops has something to do with the length of the thread cut?