Originally Posted by chris_quilts

This is weird. I use YLI all the time for piecing and quilting, including FMQ, and never have an issues except operator head space ones aka carbon based unit ones. I use mostly my 301 for both piecing and quilting with the YLI with almost no issues and used some when I was mending/darning hubby's work pants. It was what I had in the bobbin at the time. I agree it might have been the thread or might have been something else.

Chris