Hi Julen,
UCustomizableObjectInstance is a container of parameters. The virtual machine that uses those parameters to generate meshes and textures is stored in the UCustomizableObject (CO).
The hitch you mentioned (IsCompilationOutOfDate -> GetParticipatingObjects) has been fixed and will not occur starting with release 5.6.
Keep in mind that even after the fix above, hitching may still happen to some degree when compiling COs. Mutable must load all child COs to compile the graph, and when that happens, the meshes in those COs are cached, which may block the game thread. We’re working on removing this and other hitches, so expect further improvements in future releases.
Regards,
Pere