weak_maps are supposed to store variable during a single round, not between games or rounds. See session class “Type for which there is a single instance per round”
The docs say it could change in the future to one instance per game
This is actually a bug, see Verse Internal Error - #4 by im_a_lama
So I’m not sure what you’re trying to do exactly, but maybe using a custom round system instead would work better, if I understood correctly 
SEE: Verse global variables no longer working, even on previous uploads
EDIT: I’m not sure about the fact that it resets between rounds, maybe someone can help me with that
EDIT2: If that’s the case, this is something they reverted, it used to work between rounds but not anymore, this is why the “official” sample is not working.