lovingly borrowed from mal

modular_doppler/modular_species/species_types/snails/modular_snail.dm

@@ -106,7 +106,7 @@
 	return standing
 
 /obj/item/storage/backpack/snail/item_interaction(mob/living/user, obj/item/tool, list/modifiers)
-	if(!istype(tool, /obj/item/assembly/signaler/anomaly/bluespace))
+	if(storage_core || !istype(tool, /obj/item/assembly/signaler/anomaly/bluespace))
 		return NONE
 
 	qdel(tool)
@@ -119,9 +119,11 @@
 	add_filter("bluespace_shell", 2, list("type" = "outline", "color" = COLOR_BLUE_LIGHT, "size" = 1))
 	playsound(src, 'sound/machines/click.ogg', 50, TRUE)
 	storage_core = TRUE
+	var/old_inventory = atom_storage.return_inv(FALSE)
 	emptyStorage()
 	create_storage(max_specific_storage = WEIGHT_CLASS_GIGANTIC, max_total_storage = 35, max_slots = 30, storage_type = /datum/storage/bag_of_holding)
-	atom_storage.allow_big_nesting = TRUE
+	for(var/obj/item/stored_item in old_inventory)
+		atom_storage.attempt_insert(stored_item, override = TRUE, messages = FALSE, force = TRUE)
 	name = "snail shell of holding"
 	update_appearance()