The issue is not limited to the objects placed in the example mission. Most importantly it affects all classes of the "Land_BagBunker_", "Land_BagFence_" and "Land_HBarrier" families.
Simply disappearing into the ground (similar to the destruction effects of ammo boxes) without being replaced by a proper damage model would be preferable.
For mission-makers the bunkers are ideal to create outposts but with the outlined issue they are far too resilient.