while i was shaman on the event, i died i just launched a single up cannon, it kills all the mice except one, but i died, but the mouse almost fell but the mouse still wins :(

doesn't sound like a bug to me, maybe i'm missunderstanding, but i thought if any mice were left after the 3 shots/time passed then the shaman dies and the mice win? sounds here like all but one mouse was killed, and then that mouse won when the shaman died

You probably forgot to move yourself and died after 30s.

Once you spawned a shaman item (except arrows) the automatic afk death is disabled, too.