There recently has been a similar report at Cesium showing outdated google maps imagery - you might want to have a look at the answer by @azrogers there.
But based on your description, I have to ask: It sounds like you previously received more recent data, and now you are receiving outdated data - is that correct?
If this is the case, then that’s certainly unusual. There may be certain phases when Google is updating the data (which may lead to anachonistic tiles being displayed), but I’d expect the data to always and only be replaced with more recent data, and not with older data. But in general, Cesium does not have any control over the 3D Tiles data that is delivered by Google, and I’m not aware of a mechanism for accessing older versions of the Google data.