I just played a game with Wall, game 9336830. Unfortunately it can't be loaded because of an "internal error", maybe related to the bug.
I can't find this among the known bugs.
During the game, Wall was clearly influencing the point trackers, since gaining a card resulted in a 1 point reduction. But on my last turn, my score was something like 5 VP, before gaining a Province and ending the game. My opponent had something like 5 VP. Definitely neither of us had 0. But in the end screen scoring, my opponent had -3 and I had 0. Both had exactly 33 cards, giving -18 VP from Wall. I had 3 Provinces, so my score of 0 is correct. I assume his score was correct too, he had probably 2 Provinces and a Duchy. So the problem was the point counter during the game, it was somehow not counting enough minus points for Wall.