Linkage Adjustment for Neutral Safety Switch?

I have the same problem, and in my case it's a problem with the insulator being loose on the manual valve lever in the transmission.

In park and neutral positions the lever allows the neutral safety circuit to be grounded allowing you to crank the starter.

If the insulator moves slightly on the manual lever, it blocks the circuit from grounding.

I installed a ground wire from a bolt to the starter circuit grounding terminal on the starter relay to bypass the neutral safety circuit.

Only potential problem is the car can be started in any gear.