I think the prt source is rerequesting the IMaxKrakatoaPRTSource::Stream multiple times during an atmospheric render. Two times. Is this correct?
I don’t think so … Is it possible you had the node on the list twice?
I would expect to see it evaluated once more immediately at the end of the render because the viewport cache is dropped at the beginning of the render and needs to be rebuilt for display. Could that be it? My tests don’t indicate the object is evaluated more than once before the rendering actually takes place.