I have six working Grafmatic 23 holders. If the septums aren't perfectly straight, they'll be a tight fit. Usually you can straighten them. The corner near the notch is the one most likely to be bent.
Also, remove all the septums and make sure the springs are okay, and that when the drawer is pulled out and the septums are removed that there isn't a sixth septum sitting on the bottom on the left side of the holder, if you are looking at it with the slide on the right side. If there is, things have just gotten out of sequence, so you'll need to push down the springs in the drawer and slide the wayward septum into it and remove it. Cycle the holder and advance the wheel manually if the silver hook isn't in the right place when you try to slide in the darkslide, and when everything is as it should be, you can return the septums to the holder.
The wheel could be a lubrication issue. When you look at the top surface of the drawer with the holder oriented as it would be for making a photo in the horizontal position, you should see a little cylindrical wedge shaped pin, and if you move the silver hook up and down with your thumb, you'll see that it's connected to this pin. When you return the drawer to the holder to advance to the next frame, this pin is pushed down to advance the wheel. When you push the drawer in, make sure you are only pushing the handle, and not the body of the drawer, or the silver hook won't be free to move. If that's not the problem, then I think there is a Graflex service manual describing all the factory approved lubricants (I think there are at least three) either on graflex.org or the South Bristol Views website, but what I'd try first before taking anything apart would be a tiny drop of silicon lubricant around the cylindrical wedge, because that's usually what hangs up.
