Temporarily remove their pathing and after you set them reset it. Go to Art - Selectable in game and set it to False. If I recall, destructables that cannot be targeted are also invulnerable, but if this doesn't work, pick every destructible in Playable map area in the Map Initialization and if destructable type of (Picked destructable) Equal to X then Destructible - Make (Picked destructible) invulnerable.
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