This “update mpreview and metadata”, was that in RC or your developer?
Since it eventually DOES show your changes, are you still sure it’s the JPG or could it really be the RAW data now?
With my Fuji RAWs, it doesn’'t seem to work at all, even though I have the codec installed - it just stays at the first hugely pixelated previews and the blue dots on top of the 2D windows never stop cycling…