Stone, Refined Rock, Fibre Leave, Silver, Copper (don't know more or haven't tried more yet).
Same, and also items from different Refinery, Extractor ...
EDIT: New Update! I just tried to stack some of my stuff together because of the update 2 mins ago. Now items that didn't stack before do stack. Just some Stones/Rocks not (but I think those are from different planets with same color).
EDIT: And the Buying plinths look normal again. YAY!