Using 3rd January version, playing as Babylonians.
I was gifted a Conquistador from the CS Valletta which I then used to settle a city.
However the city generates negative 3 culture 'from social policies'.
I adopted the 'Authority' social policy branch and chose the one that grants culture from a garrison, and If I station a unit in the city then the culture penalty 'from social policies' disappears but I am not granted any bonus, like its cancelled out.
I can only assume that when the city is created using a Conquistador, the game creates the city and then disbands the 'unit'. This action when coupled with the 'Authority' policy which grants a bonus from a garrisoned unit creates the negative effect as the military unit disappears.
Screenshot attached, I tried saving and reloading the game but it crashes to desktop each time after 3 attempts.
Having a google of the bug shows that it was apparent in the vanilla game, I tried the suggested fix which was to disband another military unit in the city (tried a scout) but this did not work.
View attachment 402855