John Deere 6620 concave adjusting square shaft - cab side

I posted this on the combine section, but I think it is a little slow at this time of year. This question pertains to the concave adjusting shaft that goes across the width of the combine - late model John Deere 6620 side hill. I am familiar with the right hand side where the shaft is supported by a bushing welded to the sheet metal. Things have to be pretty precise on the right hand side so the rack and pinion gear adjustment works fairly well. My combine has Deere's replacement panel welded on the side already and things are fairly tight and in good condition. The left hand side is another story. The left hand side is supported by a bolt welded to a bushing. The square shaft running across the combine goes through the bushing. The bolt on the bushing raises or lowers the shaft to level the front of the concave from side to side. The problem is I found my bolt broken. I have taken the bolt out of the combine frame and the bushing off of the square shaft. Once I got the bolt and bushing off of the outside I could see that the combine sheet metal has worn some in an oblong fashion. Looks like it might have worn the eccentric immediately on the inside of the sheet metal to the shape of the combine sheet metal hole. Question is what is the shape of the hole in the sheet metal supposed to be????? Second, does the eccentric on the inside fit into the sheet metal or is it suppose to be flat against the sheet metal on the inside so it can move up and down???? This is where my eccentric shows sort of a "ridge" that fits into the combine sheet metal. If it fit, how would it adjust up and down??? How often do the leveling bolts break???? Thanks for your ideas on this matter.

The block/bushing sets against the hole in the side sheet. That way it can move up and down. The hole in the side sheet is just a circle. IT really does not matter too much if this hole is worn some. There is not much material/grain/dirt down there anyway.

As for breaking the bolts. I have seen them broke but usually following hutting some thing like a rock or block of wood. In normal operation I do not see them broke often.