Batch De-noise half way in i get this.. Error the image file is incomplete, the data of channel "RGB color" is missing

[rich0550]

everything is fine until about half way into the de noise process then this starts, no change was made to the render. its possible a render slave kicked in at this point but no settings were changed.
what is happening here? I should mention there is Vray volume grid in the scene around this point. VDB file loaded.