This applies to the 930 931 932 933..
I've seen this more than once, and a machine I am currently working on has this issue, so it's on my mind!
Ok, so the 930 was unique for a few reasons.
1. It was the first machine with an automatic needle return. Meaning the needle always stops in the up position.
2. when the bobbin winder is engaged, the needle is automatically disengaged.
The methodology for achieving both of these things was fairly simple and very effective.
The needle return, however, relies on a fairly delicate shank screw.
If the machine gets jammed for whatever reason, and the hand wheel gets forced, this is the result:
There's a thin metal disc under the hand wheel that will shear through this screw if it's turned hard enough.
Now, I don't really consider this a flaw of the machine, it's user error.