It's really weird, this smoke IS animated, but it's like going beyond 4 frame range, and drawing neighbour.
They are supposed to be animated from 8 to 11, from 12 to 15 and from 16 to 19, but it's like ... going beyond 4 frames range, to some other... and I think it's the bug.
It's like, sometimes going from 9 to 12, from 13 to 16..
And, robin, it's animated 2 times slower than any other animation, i.e. 5 frames per seconds.