[CrapShoot]

To check if an action is disabled, type g_action_info <action number> in console. It displays in console the actions current goal number and the the actions original goal number.

So, you will see that action 0's goal number will be -1 after the cave door is destroyed.

EDIT: Just updated the script to use kill_action on the bridge constructs instead of deactivateAction. Now it will be turned on in the case of a human player dynamiting it after the tunnel door, but because kill_action sets the action type as -1, it will be ignored.