Why is my smoke simulation not updating? I haven't seen this question during a search.

I have a simple campfire simulation with smoke. When I play the animation through the first time, smoke and fire both appear and evolve correctly. HOWEVER, the next time I play it through, the smoke/fire retains the shape and color it had on the final frame. It's as though once the simulation is stopped, the fire is frozen in that form for all the previous frames.
Is this a bug, or have I messed up somewhere?

My rig is:
AMD FX-8310 8 core processor
8G RAM
GeForce GTX 970 graphics card

It's being rendered in Cycles by CPU, but the problem shows up before rendering.
Unfortunately, I haven't been able to try this on another computer, or on another version of Blender.

Any ideas?

[EDITED TO ADD:]
Sorry, I have no idea how to attach a file to this post. HOWEVER, I have uploaded my .blend to google drive.
This appears to be the result of a couple things:

Negative start frame.
The simulator doesn't seem to like this, I suspect that it's a bug that negative start frames are even possible to set. (will report later)

The start of the scene animation is after the start of the simulation.
Blender only simulates when the animation is played from the starting frame of the simulation (not sure why it worked at all in your case actually).
Once the simulation is Baked or cached you can start at any point.


If you set the simulation start frame to 0 in Physics &gt; Smoke Cache and then Bake, it works as expected.