That would be the layshaft in your pic, looks like it ran without oil. This can however be fixed by removing a minimum of material off the shaft until it is nice and smooth again, either in the lathe using a good carbide tool, or even better in a circular grinding machine. Then machine, fit and ream an oversize bronze bush to match the shaft, been there, done that, works perfectly okay in the A7.
No idea what happened to the plunger though, unless it came out of it's housing and was mangled through the gearbox at some time???
All the best, Markus