My opponent and I just encountered what is presumably this same bug. My opponent tried to resign during the game, but it didn't work. Instead, I finished the game with a win (a couple turns later, on my turn), but the game did not end. Instead, after I ended my final turn, it brought me to my next hand, and it said "You may buy cards", and there were no buttons on the right for me to end my turn or anything like that. After this, both my opponent and I tried reconnecting. This led me to the state being described in this thread. I can't find a "Kick & Resign" button anywhere, and "Cancel & Resign" doesn't seem to do anything. Private browsing didn't help either.
Opponent was pedissias, Server was Tokyo (I think, since it says "Connected to Tokyo" on the connecting screen I'm stuck on). I unfortunately did not record the game number, but maybe my opponent did. The game does not appear as "finished" on Dominion Scavenger.