OK, there are two possibilities there, which I cannot see, but you can look for yourself.
1. Obviously, the vertical interlock bar is supposed to limit the armature plate rotation, which it is not doing. First place to look is where somebody suggested. Is there a roller in the shifter pin that rides in the notches at the bottom end of the interlock bar? But that begs another question---is it SUPPOSED to have a roller? That feature was added somewhere along that time frame. But if it is supposed to have a roller, but doesn't, then it will not kick the interlock bar far enough in toward the armature plate.
2. Is there a nylon bushing on the shoulder bolt in the middle of the interlock bar? Once again, not all motors had such a bushing. But if is supposed to have one but doesn't, same results as above.
3. Sorry, I don't have a parts book handy to look up and see what is supposed to be there.