Do you think that that the oil slot (kirf) in the the shaft is causing a problem? The slot is cut diagnolly. Do you think having this slot could be scuffing (filing) some of the bronze bushing off and then the filings flush out to the tight clearance area and cause the gaulling? When I look at the pics, there is little bronze on the shaft where the oil slot is, it is outwards of the slot. If you did away with the slot or ran it parralell with the rocker so the bushing wouldn't cross it, would it be better?
I still can't grasp the concept that more clearence would be better. Do we run connecting rod bushing clearance at .002? When the rocker is under load, the oil film will be sqeezed down to .0001 of an inch wether there is .001 or .002 static clearence.
If the adjusters were made with a screwdriver slot instead of a deep recessed hex hole, I think it would slove the problem with them breaking.
