I had a game where two things happened: One was that, even if I wasn't getting hit by the highwayman, the game acted as if I had one less coin than I did, e.g. it would read "5 coins" but only allow me to buy cards worth 4 or less.
The other thing was attempting to buy the City Quarter would stop the game entirely. It wouldn't let me pay back debt, it would just read "You may buy cards" even though I had 0 buys left.
Cards were: Highwayman, City Quarter, Hunting Lodge, Necromancer, Shantytown, pawn, squire, skirmisher, catacombs, guide
Thanks for the report, GrantedHanted!
The "game acted as if I had one less coin than I did" is indeed a known bug due to the game incorrectly handling debt repayment when under a Highwayman attack or on your Voyage turn (and the problem remains for the rest of the game).
Not being able to buy City Quarter is a new problem, but I guess it is related to the first, I'll investigate.
For any future bugs you may find, it would be immensely helpful if you noted down the game humber. That allows me and others to revisit the game and find out exactly what happened. That includes the cards present (which you thankfully noted), but also the exact circumstances something happened.
Again, thanks for the report!