it's 1998. Not sure about EAS ECU revision though.
On that year it should certainly remain in the locked position. Have you checked the white connectors in the passenger footwell at the bottom of the A post? The height selector wiring goes through there.
It is of course possible that the ECU has been changed at some time for an early one, even so I would have expected the inhibitor button to stop height changes.
 
Connectors in left footwell have been removed & wires soldered years ago !! I'm not gonna worry about it as otherwise the system is working fine.
 

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