I have watched the video but he never shows that particular clip. I'm pretty sure I have it back in the right spot though. I believe it goes in a small slot between the motor (metal housing) and is directly behind the insulator helping to keep it in place.
I didn't find any loose connections so far. I did find oil in the connections and cleaned that up. The commutator is unevenly worn and I don't like the looks of the wrapping. I am wondering if this motor was re-wound? I have it cleaned up and back together so I'm going to continue as if all is well and see where we end up. I have taken apart and cleaned enough motors now to feel pretty confident in what I'm doing for the most part. If it still won't work I'll have to test the motor and cord separately.