Cari, you were right!
I've been dealing with random thread nests on my 401a. I've cleaned it. I took a brush to the bobbin area and removed all the lint. I removed the bobbin case and cleaned it and checked for burrs. I removed the bottom cover and blew out everything with the air compressor. I thought it was clean.
Cari said the bobbin race might be dirty, so I did it all again. I had trouble putting the bobbin case back in, so went to youtube to see what I was missing in getting that thing back in. I pulled up a tutorial with some woman cleaning a 401 bobbin race with q-tips with a drop of sewing machine oil on it. So I tried it.
This is what I cleaned out of that bobbin race. Needless to say, I haven't had anymore trouble with thread nests.
bkay
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