my biggest issue with these old mice is the cord , the wires break apart inside from the movement of the mouse over the years, I just hack off about 6 inches up, reuse the rubber snubber, pull or drill the old/bad hunk of wire through it. Thread the trimmed mouse cord back through the snubber. Then strip / knot and solder the wires back to the mouse pcb. never had mouse guts them selfs go bad… well not yet