"damaged or improperly lubricated input shaft splines, "
The bushing must be pre-treated before installation. Sintered bronze ( if thats what you call oillite) bushings have porous construction that allow the ingress and containment of lubricant. Before use it would be soaked in a small pot of motor
oil for 24 hrs or so, then it's a good idea to squeeze
oil through it. If you need to install a new one and don't have time to wait, sit one end of the bush on your thumb, fill it with
oil, then squeeze the other end of the bush with your other thumb. This will hydraulic the oil through the bushing pores, you will see it sweat oil from the outside of the bush.
Old mate taught me to never ever use grease on the input spline, this can cause the disc to not slide free. We always used graphite powder or similar, but with all this new fandangled modern stuff around I have been using a very thin smear of Never Seize on the input shafts last few years.
Both these things have worked for me the last 30 years.
Good luck with it.