I've noticed if a city is unable to build an improvement due to low materials or insufficient space that if I correct the issue, I'm unable to build anything until the next turn. For example, in the below screenshot I did not have enough materials at the start of the turn to build a garden. However, I cancelled a few units in other cities and freed up the materials (hence the 54 at the top) but notice the garden (bottom left) says it needs 35. I have enough atm but can't build it. Just a minor polish issue - not gamebreaking by any stretch of the imagination.
