When ever a selector ring doesn't lift, I tend to look at the pawl magnet circuits and the like. I suspect you have a mix of this, as if its moving then the stop dogs have lifted. Maybe a mechanical break but unlikely. As to the speed has the sls's turned over properly? I cant remember the what you call the motor(pawl magnet motor?). Not sure what the short is and I would fully investigate 'why' there is a short and 'what' the short is going over, as that tends to give a hint at what is the problem. I don't know what those numbers represent but look them up. This is of course depending on the type of selector.

I'm with Uppo.

Start with why the pawl magnet assembly. Is the magnet (coil) energizing? Is you advancer panel functioning? Once you find out if your PMA is electrical or mechanic then move on.

I'm not positive? But I believe c51 to c59 is a "SS" switch. Are your speed relays picking?

It sounds like one of the 6850 selectors. I had an 8 car group for years. We finally modernized them. But to give you an idea of how long ago that was! We installed Swift-5000 controllers when they first hit the market.

Have you checked voltage at the coil that lifts the ring? I have had the coil it self go bad.