This sounds like an out-of-memory situation. Checking here, I do see that memory usage is creeping upward with each export, but I cannot speculate, before doing some research, what might be the cause. I would recommend making sure to use instances where possible, using the Cache Meshes option where possible (i.e. if only the camera is moving), and as a last resort, exporting frames 0-20, then 20-40, and so on, as a last resort.
Also note that the .jpg (or whatever) images you see are just placeholders to make Bongo believe that the frame was successfully written (it would stop animating otherwise); this being Maxwell, the actual images will only be created when the MXS files are finally rendered in Maxwell Render, after the animation export is finished.
Next Limit Team