No rattling from the bobbin, or bobbin area, on mine. But then, the jib was flopping around and I had to take the whole thing out to found a screw was put in from the back by a previous "enthusiast" (also used white lithium grease on the gears, ugh). I was lucky enough to get a bunch of vintage bobbins with the machine, so I haven't tried a newly manufactured one in the case yet, but they might not work as well. The new bobbins are made like 15 style bobbins, with a ridge, so that might be noisy. Or your bobbin might be bent a little.
Just a few other things to consider before trying to take apart the bobbin case. Scary.