There are a problem with that backpacks. They are losing their protection (as default they are undestructable)

Merged post

UPD: There are one thing in plugin for change base protection of entity

private void SetupProperties()
        {
            var entity = GameManager.server.CreateEntity(prefab); // one specified prefab
            if (entity == null)
            {
                return;
            }

            entity.Spawn();
            var combat = entity.GetComponent<BaseCombatEntity>();
            if (combat == null)
            {
                return;
            }

            // Heat
            combat.baseProtection.amounts[5] = 0.8f;

            // Bullet
            combat.baseProtection.amounts[9] = 0.9f;

            // Slash
            combat.baseProtection.amounts[10] = 0.5f;

            // Blunt
            combat.baseProtection.amounts[11] = 0.5f;

            // Bite
            combat.baseProtection.amounts[14] = 0.0f;

            // Stab
            combat.baseProtection.amounts[15] = 0.5f;

            // Explosion
            combat.baseProtection.amounts[16] = 0.0f;

            PrintWarning("Properties was setup!");
            entity.Kill();
        }

and looks as it worked for all entities in the world