Well, I took it apart again and redid everything including taking out that shaft. I also played with the service station to see if anything that I could see looked out of place because of my enthusiastic cleaning. I put the printer back together (I'm getting faster with this!) and still got the Error 21:13, and in scrolling down on the front LED, in some of the cryptic terms I found "jam" mentioned.
There is also a black plastic cover that emerges and sits over the sponges. It was only partially visible, but thickly coated with black ink. When I turned the printer on again, it extended fully to cover the sponges, and while the printer tried to initialize, the service station (or part of it) moved toward the back of the printer and back, but the sponges never got exposed, and the Error 21:13 popped up again.
Wanna buy a fixer-upper, cheap?
The saddest thing is that I used the printer to make between 4 and 10 prints a week, if that. and it was certainly not from heavy use that the belt self destructed. And with so many of the LuLa people reporting crumbled belts, all at about 3 years of use, whether heavy or light, it seems to me that something is amiss.
The printer seems built to be a workhorse, and I don't think HP purposely put a belt in that is 1) so likely to die early, and 2) requires such amount of work to replace if they knew it would go in 3 years. I think either they got a belt made of materials not meant for the stresses, or their printer design leaves something to be desired.
I tried fixing it myself because I could not see spending the $1000 - $1200 that people report being charged to do the job, and if it were a car instead of a printer I would hope the company would do the repairs as part of a recall, or at least an acknowledgment that the part or design was faulty.
In all seriousness, I'm stymied at this point. I don't really know what to do.