Singer heavy duty brand new
I carefully threaded according to the instructions.
I did several test seams the were beautiful.
Started working on a project.
Now the under side is a rats nest of tangled broken threads.
I’ve rethreaded the machine presser foot up.
I’ve reinstalled the bobbin.
I’ve held slight tension on the thread tails.
None of this works. I still have a mess of ratty broken threads on the bottom and mangled fabric.
This is literally a brand new out of the box first time being used machine.
What am I doing wrong?