Quilting, projects, family...life!
I do a no-no thing and open the bottom part of the arm, too. I do a deep clean after every major project. I don't understand the lint color, either. It doesn't match my thread. I quilt my own, so I am assuming it's the natural accumulation of dust on thread, fabric, and batting (despite keeping it all under cover). Plus bits of batting fibers.
Thank you so much for taking the time to comment!