I keep a hand vac ready to go between my two machines. The other day I cleaned that bobbin area at least 3 times and while it still sewed okay, I could tell by the sound there was some junk in there somewhere.
I looked, vacuumed, tried pipe cleaners, brush, pulled all apart that I could, wiped it with a nice clean cloth, put it back together. Sewed great for about 6 inches and there was the noise again!
I figured I'd try one more time and if that didn't do it, I'd sew until it broke. Then we'd be able to see what was causing the problem. EXCEPT this time, I taped part of a toilet paper tube to the end of the already small end so it was just a smidgen of suction area. That did it!
Wherever and whatever it was just popped right in there and it's been great ever since. I have no idea where that "piece" was lurking, but it was big enough to make a sound!
I immediately ordered one of those small area tube attachments which came today and is even smaller than my toilet paper tube one.
My little Fuller hand vac and I are getting to be great friends.