This is a very common frustration point for many sewists when sewing with a sewing machine and even more frequent when doing machine embroidery. It is referred as Bird nesting as the tangled thread ...

Question: Can you tell me why, when I come to the end of a seam, the threads get bunched up on the bottom layer? It doesn't always happen, but when it does, I find it so annoying. _ Mrs. K.N., Prairie ...