Is there no way to reduce the flickering of distant glowing spheres? They are way closer to the camera than the smoke, so it's not the camera distance. What else could be causing this flickering? Anti Aliasing? This only happens when the camera moves.

Well... had no choice but to increase Anti Aliasing samples to 3. That slowed the rendering down considerably... Might as well mix the already rendered images with the new ones to stop the flickering and save time.