I have had bugs with additional brothels:
-the naming of every brothel beyond the second - everytime, it is the second brothel that is renamed, I have got around it by modifying the save file directly.
-I have had, once, a bug when I bought the sixth brothel:
1. It did not check the conditions (I could buy it the same turn I bought the fifth, with only 140 businesses)
2. Instead of giving me the "real" sixth brothel, I had instead the image of the first brothel, the introduction to the city - in fact, it was as if the game had generated a sub instance of itself - when I clicked on "Quit", I went to my five previous brothels.
And now I've tried to reproduce it (after the reload), it lets me buy the 6th brothel (though I have only 141 businesses), and the 6th brothel behaves as expected, except that when I click it on the town map, it tells me that I should have 170 businesses and 25k gold to buy it.