There's not much to the assembly itself. The armature fits in a groove if I remember correctly, and I believe there is a small plastic piece (or rubber) that creates a snug fit. It's pretty obvious when you look at it. (not visible from your photos - it's on the other side of the metal bracket)

You should be able to move the motor shaft by hand. Mine was siezed up. If the shaft turns freely, check to see if you are getting voltage to the motor.

This is all from memory, as I'm at work and it's been over a year since I've had any reason to get inside my TFTC.

But I think I ended up using a shooter tip rubber or something similar. Just pop it on the end and it snugs things up nicely. (edit - actually think I just put a small round post rubber over it and it fit perfectly)

Not gonna make a difference if the motor is shot, but I'd still do it when you fix it up. Good luck.

The arm should clearly move an inch or two when you engage the motor, as long as the arm is attached to the motor shaft. You are really dealing with basically a 3 piece assembly - the motor, the arm (which locks into the tombstone) and the tombstone itself. So there isn't much there to be missing.

If it's just sitting there kind of "grinding", I'd assume the motor is siezed up.

I think it took me about 15 minutes to pull and replace the motor. I'd remove the motor from the assembly, then run the tombstone test. It will give you errors because the switches aren't being made, but you should be able to look at the shaft on the motor and see if it is turning.

If it turns freely, you may be missing something or it's binding up somewhere. But if it just sits there "trying to move" - time for a new motor.