When i choose color and then click on an object to paint it, then it works usually, but sometimes it just doesn't.
I think it's more likely to not work for roof objects in Buildings section. If it doesn't work once, then it never works on this object, no matter how many times i click. However clicking from other sides does work.
Also after painting operation failed for one object, there's a chance it might not work on other objects, at least for some time.
That's all the information i was able to collect