First machine I received clanked when I stitched.
After trouble shooting with you, had to send it back.
Received a replacement.  It did not clank, but the stitching was off.  After trouble shooting with you, it has to be sent back.  
My concern, is where is the “quality control” ?
I am hoping 3rd is a charm.  
If not…..no more returns for replacement.  I’ll ask for a refund.
This should not be happening.  I have always used Singer machines, but this experience has me questioning just how good they are these days.