In a game against a bot I had AutoBuy set to "on". I was in my buy phase and had played treasure to the value of 4 coin and 1 potion. Since I had 1 coin token, the Duchy pile had the little "+" sign showing I could buy from it. I clicked on the Duchy pile and the game client went "belly up" in the sense that it didn't continue the game. The "+" signs were removed from the piles, but otherwise nothing happened (see screenshot). I could undo without a problem and repeat my action, to the same effect.
The game is #1387723 and the decision is 202 (beginning of that buy phase). The following behaviours from that point work as they should be (getting me the Duchy and continuing the game):
1) Clicking on the Duchy immmediately.
2) Clicking "Autoplay Treasures", then clicking on "1 Token" to explicitly change the coin token into 1 coin, then clicking on Duchy.
What does not work (the scenario I encountered) is
3) Clicking on "Autoplay Treasures", then clicking on Duchy.
The bug ist still present in version 1.1.2.
My suspicion is that the bug is somehow caused by the interplay between potions and coin tokens. The bug can again be found in game #1419628, decision 70. In the same game, at decision 25, a very similar situation works as it should be: I have 2 copper and a silver in hand, no potion this time. Clicking "Autoplay Treasures" and then clicking the Duchy works: My coin token is used to get the 5th coin needed to buy the Duchy.
This happened to me on game #2242028 on frankfurt, but with $7p and coin tokens, buying a province.
Another data point I guess.