Two possible related issues you can check:
One i recently reported which is targeted to be fixed soon, related to where your root is: [CRITICAL] Scene Graph child meshes disappear when placed far from root entity
Two: Related to spawning but solved them by using a creative device to spawn entities and not doing addentity through sg entities/components.
world_creative_device_reference<public> := interface:
AddEntitiesCustom<public>(ParentEnt:entity, Entities:[]entity):void
AddEntitiesCustomSimEntity<public>(Entities:[]entity):void
MYDEVICE<public> := class(creative_device, world_creative_device_reference):
AddEntitiesCustom<override>(ParentEnt:entity, Entities:[]entity):void=
ParentEnt.AddEntities(Entities)
If that doesn’t work try adding to sim entity:
AddEntitiesCustomSimEntity<override>(Entities:[]entity):void=
if(Entity:=GetSimulationEntity[]):
Entity.AddEntities(Entities)