Periodically, it needs both the mode switch and the leaf switch
that detects the cassette write protect knockout De-Oxed.

The write-protect switch is working, because the unit auto-ejected a
cassette with the tab removed, while accepting one with its tab intact.

I don't know where the mode switch is, and I'm trying to postpone removing
the transport board.

The unit is a remarkable piece of "less is more", especially considering its
plethora of features, prominently splashed across the front panel.