Good stuff Ving
Was it quite windy when you were capturing these shots?
I was out the other night in windy conditions also taking Jupiter shots and all the resulting images I processed ended up with onions.
As far as I can tell windy conditions almost always produces onions.
I think it varies the quality of the frames by such a degree, particularly towards the planet's limb, that when stacked they produce onions.
It's just my opinion, but onions are the result of exposure variation to which windy conditions can certainly make a significant contribution.