Did a 125km ride today and the play did not come back. So for now the 9Nm on the expander (higher than recommended) and the 5Nm on the stem bolt seems to hold.
I think i'll give it a try too, but i'm not sure that is what my problem is.
I did 6.5nm on the expander, and 6nm on the stem bolts and i still have some play after my ride.
But upon inspection it seems like my expander plug did not move, but just the stem maybe? I'm not sure if I should add some carbon paste on my stem. Anyone has suggestions?