Keystoner, i think i have bypassed the problem with a hotwire direct to the solenoid, which seems to work every time if the key operated starting does not.

It is such a PITA to change the starter, especially in the dead of winter, that i think i will go with the hot wire, and maybe an auxiliary pushbutton. Since the problem is apparently in the ignition switch wiring, i think a rebuilt quality unit will have the same problem.

But i am definitely saving the old Bosch starter for next time. It needs a solenoid.