Dino Starter Engagement Issue

Started having this problem with my starter engagement. Sometimes engages and starts right up but more often takes 10-15 times to get it to catch and turn the motor over. Original solenoid contacts and gear look like new. Ring gear looks like new with no chewed teeth. I put on a NOS solenoid, same problem. I put on another starter, same problem. Plenty of power from the battery. Only thing I can think of is maybe the alignment of the starter gear and the ring gear went bad though I don't know how that could happen. Maybe shimming one side of the starter to gain a little clearance? Any thoughts on a solution? I made this short video of the problem:

 

I have done nothing to the car. This just started up out of the blue. Wish I could get an inspection camera in there to see what is happening. I may paint the teeth of the starter pinion with Prussian blue and see if that shows a meshing problem. It never grinds, just doesn't engage.

 

Here is an inside view of the starter action. Seems I am getting solenoid pinion engagement but only occasional starter rotation. Again, two different starters with new solenoids. This is a real head scratcher for me. Only thing I can think of is the solenoid contacts are only slamming together once in a while for some reason.

 

Steve, thanks a bunch for your input. It was the almost new Ghibaudi starter drive that was bad. Put in another new Ghibaudi unit and works great. I hope that was just a fluke but my guess is it is an under engineered part. The original Marelli unit looks more heavy duty.
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