I was thinking along the same lines with a dirty contact in the switch, but you think with several attempts of moving the key back and forth that the contact would make up once in a while. Even hitting the column might help.The AA used fusible links up until the end of production. I own one of the last Spirits built, and she's got fusible links. No relay center, either. They're all over the place in these cars.
I would be tempted to look at the switch over fusible links-- a fusible link is essentially a fuse built into the circuit and is typically either blown or not blown. Switches are much more likely to go intermittent.