Birds nest
At one time, it seemed like just about everything I did turned into another birds nest. After lots of posts on this site and getting help (thank you all for your suggestions) it seems that my problem was the manner of filling the bobbins.
Even so, I still get a nest from time to time and it generally happens on the final block of series and very close to the end of the stitching! I got a one piece knife kind of thing that is flat and supposed to slide under the hoop to cut the threads. Don't get one! They don't work. Too short and more dull than my kitchen knives! I generally end up cutting holes in the embroidery and basically ruining any chance of finishing the block.
Last week, on a website that I can't remember the name to give credit, I saw a tip. To get rid of the birds nest without ruining the embroidery, remove the pressure foot. Duh! Obviously I never thought to do that. When it happens again, and I know it will, I'll give it a try and let you know if it helps.