Maya :: Referencing / No Update In Referenced Scene

We make a small Animation Movie and from time to time we stumble upon strange behaviours of the referencing pipeline.

There is a Kitchen that will be the scenery for the Movie Scene Set up: all models i.e the toaster, the fridge ansd so on are modeled and saved.then in the Kitchen File we have an empty scene where all the objects are referenced in. thats the "model master"scene.now we referenced the toaster_model into toaster_shaded, did all the shading and changed the references in the kitchen from toaster_model to toaster_shaded.

On some objects we noticed, that the updates made on the models for examlpe if we scale up the toaster on 2 and freeze transforms afterwards, the change is not updated in the Kitchen file. But after a few days the update works...

System:
AMD x6 3.2Ghz
16gb Ram
Nvida GTX 460SE